Talking from my own perspective, I often get my sense of worth mixed up with with a sense of success and popularity. Nonetheless I do believe that it's important for general feeling of happiness and belonging that I try to keep these separate.
My reasoning is fairly simple. Whatever my plans and intentions, life might not end up as I want it to.
I might get sick, not manage to acheive certain things, not get to do everything on my many grand lists.
The world is infinite (or at least very very large); I could spend my entire life in a city like New York and not know most of it.
I'll get old, and my abilities diminish. My body will deteriorate, according to those internety graphs out there it already is (I'm 25 now, aka past peak).
I can learn to front lever, back lever, do a gazillion pull-ups and do all sorts of impressive handstands and balancing manouvers. I can read tons of books, watch a bunch of movies. But! I can't catch them all.
Some skills are good things to be able to do while they last. Some display strength, virility, power, ambition or what have you. Some'll help me impress people and make me feel good because I know them. Some'll help me build a life, my own life, and may even "get me far". They're akin to add-ons in a video game.
And, they'll be there when I most need them.
Until some day some of them won't anymore.
And when that day arrives, and for most skills and abilities I know that it certainly will arrive, I don't want to feel like I'm failing and that I can't contribute anymore. I don't want to feel like my life hasn't amounted to anything because I can't do all the things I knew how to do before. I cannot let my past be more important than my present.
When I change. When my body and my world change. I still want to feel good about myself. I want to feel proud and happy about the things I still get to enjoy and know how to leave it at that. (The importance of this last part is one of the most important lessons my mother taught me, and for which I'm extremely grateful.)
So, I try to keep my goals, aspirations, success, popularity etc. away from the core of my identity.
And rather think that I do all the fancy, shiny stuff for fun, and because I'm able right now. But I don't get tangled up in my own tango and let myself believe that my level of achievment matters more than my current enjoyment of doing them.
I try to not judge myself and others too harshly for not attaining ever higher peaks of performance. And I try not to de-evaluate people based on such notions.
This also applies the other way around: I try not to feel stomped on and decimated when I meet, read or hear about smarter, nicer, richer and more aesthetic people than me.
I try to stay humble and accept that deep down I suppose we're all the same in the ways that matter most in life.