I'm 35 and overall am feeling at the top of my game. I don't envy the 20 years olds or feel lost. I've learned so much, not just technically but around user and enterprise needs, inter-personal skills, and about myself since I was 18-20 that I absolutely feel better suited for success.

I've started eating right and working out, which has helped both body and mind, and I've developed task and time management techniques that work for me. While I admit my mind might not be 100% as quick as it was when i was 20, I do feel remarkably more productive.

Although to be fair, I'm not in the SV ecosystem, and run my startup (although after 8 years maybe not a startup any longer?) from outside of Boston (a location where a strong business model still beats a profitless pitch deck), so perhaps the environment is one reason I feel the way I do.