I appreciate what you wrote, OP - moderating my ambition is both essential to my mental health and an ongoing process. I do not exaggerate when I say that in my case I believe the stakes are life and death.
One thing that has helped me a lot to find peace here has been becoming a father. Culturally, it comes with a kind of license to finally just accept mediocrity which I find freeing. Bills are paid, I can watch my son grow up, doesn't matter than I'm not the best at anything.
Child rearing does not last forever though, and if you practiced nothing for those 20-30 years you will fall into the same traps again. Accepting mediocrity is not freeing when it leads to giving up all efforts (And that’s a recurrent scheme)
One thing that has helped me a lot to find peace here has been becoming a father. Culturally, it comes with a kind of license to finally just accept mediocrity which I find freeing. Bills are paid, I can watch my son grow up, doesn't matter than I'm not the best at anything.