I know, we'd all tell ourselves to invest in Apple, and that sort of thing.
I'm talking about lessons you've learned as you've gotten older that might have done you some good in your younger years. Or things that if you'd known to do them (or not do them) when you were younger, might make your life better now.
I'd tell myself not to eat sweets out of habit, not to assume automatically that I was going to fail at certain things, and to be more willing to try things that scared me.
What would you tell yourself?