The last time I really got myself into this mindset, I went for a gravel bike ride on a day I really shouldn't have due to fatigue and having nothing in the legs, then lost it on an easy corner and fucked up my arm and hip on rocky gravel. Ended up having to take two weeks off the bike due to injury.
You don't get stronger from working out. You get stronger while recovering from working out. That's why a lot of pro cycling teams have been investing in sleep tracking stuff, to make sure everyone's getting as much rest as possible to recover from all the hard training they're doing.
And any experienced mountain biker will tell you that the second you say "one last run for the day" outside of a competition setting, if you're smart, you've already done your last run for the day. At that point, you're fatigued and already thinking ahead to dinner and getting in the shower, and that last run is gonna go sideways fast.