You going to wonder about the roads no taken, and the ones you took. You'll work real hard for things, that once you get there, you're going to ask why you worked that hard, because it's not what you wanted, expected, or needed.
You're going to trust people you shouldn't, and not trust people you should have.
You're going to believe people you shouldn't have, and not listen to people you should have.
You're going to fall in love with the wrong person, pass by a few that may have been right.
Your going to do things you shouldn't have, and not do things you should have.
Your going to ignore some really major things, and pay way too much attention to things that will never matter.
But the hope is, that as long as it's you, you can learn from that and change it.
Believe me, its much, much worse than pessimism to blame others, society, fate, culture and all the rest, cause you can't do anything to change that stuff, so it just repeats endless, and powerlessly.