How do you deal with being "sure of yourself"?

Stay intellectually humble. It's a huge component of wisdom in my observation. Understand you can always make mistakes that can be corrected, and that you have arrived at your opinions through limited information that can always be supplemented, so stay open to both of these possibilities.

You can be confident in your opinions that you arrived upon through spending a lot of effort thinking about them, and you don't need to have self doubt when challenged on them baselessly. But when someone does point out an error or something you missed, it's essential you haven't become closed to accepting it.

Always remember what the basis are for your opinions and how well-founded they really are. For example: how much do you actually know about a thing when you're relying on something you read in the news? How much do they really know about that thing?

As a check on yourself believing you've put a lot of effort into thinking about something, be on the guard for unwarranted confidence. If a professional has put their efforts into something in their field of expertise they've spent their whole lives working on, chances are you haven't thought of something they haven't in the first five minutes of hearing about their work. That might seem ridiculous, but you see this all the time on Lemmy, where for example commenters seem to think they've figured out key errors in scientific papers after reading a single popular science article about an experiment or figured out solutions to incredibly complex problems like fair taxation.

I don't. There is no absolutely "right" answers, we just need to accept the bad choices and move on. Like anyone else, you will choose the wrong choice eventually, and that's is fine, just learn from it.

It's always good to have self doubt, it leaves you open to changing your mind. Do what you think you should, but those who realise they are fallible will more easily change their view of things when proven why they should.

There's a line in Nicholas Roeg's movie Insignificance that has stayed with me for decades now.

There's an obvious Einstein expy just called "The Professor." At one point, he's asked why he's so cautious about his claims - why he habitually says things like, "I think that..." or "The theory is that..." or "One might argue that..."

His response is, "If I say 'I know,' I stop thinking."

That, IMO, points to the primary answer to your question - don't try to remove self-doubt. Nourish it. Revel in it. Because it's the thing that will keep you thinking, and the more you think, the more likely you are to get to actual truth.

I completely agree, and I try to frame my opinions like this, and be open to me being wrong and accepting better information. I don't do it perfectly 100% of the time, but I do try, especially in a work setting.

One thing to be wary of: some people will call these humble qualifiers "weasel words" and accuse you of lacking conviction. Most likely to happen if you're having a political discussion with a person who's convinced themselves that they have it all figured out and/or they mistake bullying for a good argument. I try to disengage with that type of person, but they're out there in the wild.
- Yes - I've had many of those asshats over the years insist that I have to "choose a side."
  
  That's generally because they can't actually argue for their position, and the best they can manage is to find fault with a self-serving characterization of a falsely dichotomous opposing position. So they need to be able to assign me to one or the other team, so they know whether they can ignore me or if they need to hurl some emotive rhetoric and fallacies somewhere in my general direction.
  
  And yes - they're almost never worth engaging with.
  
  And to go all the way back, it could be said that the exact problem is that they have unfounded confidence.
  
  And it's sort of ironic really, because they're generally driven by a psychological need to be right, and clinging desperately to one fixed position pretty much guarantees that right is the one thing they will not be.
This is great. It's a nice little addition to a list of gratitudes.

I don't think you should ever fully remove self doubt. It's useful so you don't end up a megalomaniac.

But generally speaking, you do the best you can. I look at the situation, weigh the variables, and make a decision based on the best information I have at the time. If I'm wrong, I'm wrong.

It's sort of like playing poker. Sometimes you have AA and you lose to someone with 72. Doesn't necessarily mean you misplayed the hand - sometimes you do your best and still lose. Just lick your bruises and keep moving forward.

Also, I think being able to admit to your mistakes when you are wrong will help a ton.

I always know I can never be 100% sure of anything. That removes some of the pressure of needing to be right, and ironically some of the uncertainty too. Other than that, well, just gather as much information as possible and go for it... Then don't look back

Imo, you don't. You must remain humble and open-minded.

Find a friend who you can trust to be honest with you to second guess yourself with—preferably someone with a lot of emotional intelligence and self-awareness.

It's important to look at the reactions you get. If what you're saying provokes discomfort or hostility, that's the time to reëxamine what you just said.

And further, when someone disagrees, try to politely ask why. Most people are willing to explain where you fucked up a long as you don't get defensive.

This gets a little tricky though, because other people's reactions aren't always a good metric. If multiple people are telling you something, then it's almost certainly pretty pertinent to listen. If only one person is telling you something, it's probably worthwhile to reflect on that in most cases, but you may also want more feedback before you go too deep down that rabbit hole. But this all depends on the people you're around, what kind of criticism/feedback you're receiving, and what's behind the other person's intent for telling you.

Sometimes we end up in relationships that involve gaslighting and emotional abuse, and it's not always obvious to us. Sometimes, we don't have a strong sense of self and we look outside of ourselves for validation more often than not. Sometimes we interact with people whose internal experience is wildly different from our own.

IMO, it's important to work on strengthening our egos when they are fragile, and to form our own foundational sense of self from which we can build atop with feedback from others.
- Reading other responses, I think maybe I misunderstood OP. I thought she was asking, "Self-assured peeps, how do you self-monitor for arrogance and egotism?", which is where my advice is coming from.
that’s the time to reëxamine what you just said

yeah this is definitely hard, I feel like sometimes it is hard to see what caused it. or overthinking on what is it that provoked. and then focusing on probably the wrong causation and then basing everything afterwards on that.

Genuinely asking, Do you usually ask for clarification even on that or not? I feel it would make it worse, "What did I do, to make you say that just now to me?" I would normally think it comes off as arrogant.

someone disagrees, try to politely ask why. Most people are willing to explain where you fucked up a long as you don’t get defensive.

Yeah, the problem is sometimes, the experiences don't match up properly and the explanation will still not fit the reason for disagreement. Navigating past that, is really difficult. Because I feel it then becomes a battle of egos. Because all points on the table, self-included, will not fit the solution. But, I guess maybe in these situations a third party is necessary?

I think in this context it's important to be specific about the type of self-doubt you're experiencing. Are you unsure about something specific you're stating? A decision you're making? A belief you have? A pattern of behavior you exhibit? Yourself/your life in general (literally, "unsure of yourself")? These are all separate things imo and warrant different levels of healthy doubt. Like, be open to being wrong about a fact, and be mindful of your behavior / willing to change it if it's hurting others, but no need to spend energy constantly doubting who you are or how you're living your life. Whenever I experience self-doubt, I try to first ask myself which of these categories it belongs to, and based on that I decide how I want to respond to it.

I hope this makes sense, it got rambly lol

It definitely makes sense. and that's what makes it more complicated. because it is also hard to relay context to get second opinions. sometimes what's left is personal reflection, but practicing how to remove self-bias and not re-adjusting past memories to fit an argument is very difficult.

Thank you for listing those categories, it's nice seeing them out in print to properly remember.

I double check. If I think that I'm right about something, I take a moment to consider "have I actually double checked this to make sure it's true? If not could I potentially humiliate myself by saying something verifiably false, or could I potentially spread misinformation? If I haven't checked, then I take the time to look into it first before trying to talk about it or make any claims about it. I try not to go based entirely off assumptions or gut feelings. If it turns out I was wrong, then I've learned something and avoided a mistake, if it turns out I'm right, then at least now I know for sure that I really am right. It also helps to get into the habit of actually thinking about what I'm going to say, whether it's actually right or not or just feels right without anything to back it up, and to be open to being wrong. I try to see the possibility of being wrong as a potential learning experience, which makes it less scary, and also makes it easier to not cling to the desire to be right all the time.

Yeah, I also tend to log everything that is supporting my argument. But, it definitely feels like it could be worse "gathering evidence" sometimes. Especially if the topic is around self-improvement rather than something objective.
- If the topic isn't objective then I try to keep in mind that just because something makes me uncomfortable or I disagree with it, that doesn't automatically make it wrong or me right. I have to contemplate why I disagree and whether it's something that actually affects me or just something that rubs me the wrong way for no good reason. And if something does bother me, is it productive in any way to make that known to others or should I just keep that to myself? And even if it bothers me, does that mean other people should be bothered by it too? If yes, then why? Is it a morality thing, or just a personal preference thing? Then even if it is a morality thing, I don't have to try to make it an argument or a fight, instead I can just try to get my own views across and explain my reasoning for the other person to make of what they will. Doesn't mean I never get mad or into fights, but I try to usually just give the energy I get.

You don't

Simply keep saying "Fuck it we ball" untill you can ball no more

OP: I'm struggling with mental unwellness how do I deal with this?

Every reply: You know you should feel even more unsure of yourself, you're literally wrong about everything and you're also probably really dumb.

Therapy and anti-depressants

Edit: tbh, I see how the question is framed as a general question too.

I think overall, therapy is a great solution. I wish it was easier to start the process in the states. Surprisingly I haven't had any experience truly understanding anti-depressants or being close to those that took them and were open talking about them. I wish I knew more about their effects on how they help with self-assurance.
- Depends on the person or the medicine. So your results may vary. Basically anti-depressants for me lessen the impact of depression. So when the idea pops into your head that that is negative or self doubting it's easier to reflect and evaluate if that thought is correct or not. As well it helps with break negativity chains where something goes wrong and a bad mood continues for several events. That is a confidence killer.

By not being sure of myself on anything except subjects about which I have done a great deal of research and reading and/or have considerable personal experience and knowledge. This means that I am not "sure of myself" very much, and when I am, I feel justified in doing so

I doubt literally everything and don't trust my own judgment. I'll thank my ex's affair for part of that.

I hope that someone else in the room will challenge me.

You really don't maybe you shouldn't. I just try to compare new things to things I have done in the past and evaluate how much effort more it will take. At work for example: every change is 2 days. You want the little light to be green instead of red? 2 days. You want to change the programming language? Still two days. On average it works out. You just keep stacking successes behind you gradually taking on bigger and bigger tasks. Each one is only slightly harder than what you have already done.

When the self-doubt is overwhelming, a gambler's desperate bet is made, to go all in hoping for a miracle.

When forced by circumstances, whether as a hero or a villain, one becomes the protagonist of an epic that foretells the rise or fall of an entire world.

When everything else fits perfectly into place, being right is the only truth worth considering.

Sir, this is a Wendy's...I just need to know what you want to drink.
- Oh, uh... Water please. Thank you.

I'm perfect, it's impossible for me to be wrong. ;) I can get additional facts and have a need to change my point of view, which is called learning.

At least at my house I got told loads of times that nature gave me a brain, so I should use it. So I'm always right... with the knowledge I have at that time. I'm never proven wrong, just that I lack knowledge. ;) (And from time to time I learn loads)

Similar to this: I never question my past decisions. They were most definitely correct with the information I had at that point in time.
I can learn additional facts about that thing, but it's pointless to question myself about my past decision because back then I didn't have all those info I have today.
So my decision could be different today, but it was most definitely correct back then.
Therefore no self doubt, or just very rarely.
- You can definitely make decisions that you later feel were wrong, even taking into account the limited information you had