I think I'm nicer than I was in my youth, as I understand people a lot better and see everyone as the flawed, insecure, damaged people they are. I'm a hell of a lot smarter than I was back then, and I don't miss most of that rampant stupidity. I'm not sure I miss the mindset as much as I miss what mattered to me, which was writing antagonizing papers, partying and women. What was there to be really stressed about?
Did I change or did the natural progression of life occur? Responsibility is heaped on you, you can't go out every night, you have a job, then a spouse, then a home, then kids, grandkids, all of these responsibilities to juggle. For a lot of people, its easy to get caught up in that, to not have fun anymore, because there is so much to worry about, you can't really relax. You get cynical, resentful, whistful and nostalgic for times that were "fun" and "carefree". I get that. We all get a little jaded over time. But really, my wife has a sister who is 15(She was a mistake), I don't look at her and go, "Ah, the innocence of youth", I instead think, "You are an idiot, but that's ok right now."