I'm in my early 60's, and I don't think there's much I'd change in my past. Made some mistakes, and like I've heard it said: "We learn from our mistakes and the worse the mistake the more we learn". Read that to mean that I've leaned a lot. As for marriage, I got that right. Been married for 40-something years to the same freckled redhead, and it's been 3 of the best years of my life (She hates when I say that).
I wouldn't have sold the Marlin 336T in 35 Rem that my Dad gave me when I turned 15. Even today I can't understand why I sold that rifle.