I would have bought AMD when it was at $2.
Seriously I would have made every effort to have a child with medical help when we determined I might have fertility issues from a ruptured, abscessed appendix. If I had pressed every effort and spent the big bucks earlier, I might have more children today. (Love the one I have, always wished to have two.) Of course, we didn't have the big bucks, and medical science wasn't where it is today, so maybe the effort would have failed, but it's a regret even so.
I'm 50ish, and I wish I knew at 20ish or 30ish that it's really okay to be single, that a relationship is awesome if it's healthy, but also that you are far lonelier in a bad relationship than you ever are single.
Also, that life is short, and don't take it all so seriously.