Not me. More than half of my 20s were mostly defined by working service industry jobs, hanging around with party kids, staying awake until the sun came up, and basically getting by doing the bare minimum for everything. It was probably the lowest point of my life cognitively. It wasn't really until sometime around my mid-30s that I started feeling pretty sharp and performing well on cognitive tests. I didn't grow up in an environment where there were any cultural expectations of achievement in anything. I had to find all of that on my own through a lot of trial and error. That being said, who knows where I would be today if a nice chunk of my 20s had been less dumb? I ruminate about it fairly often.