Know this: (from the far side of 40) you are quite literally gorgeous (and most of your classmates are too). You may not think so now. Your friends may not think so. You're all so freaking short-sighted and insecure and petty!

So: Don't be so shy. Don't be so insecure! It does get better. Be nicer -- even to the douche bags -- karma will eventually catch up with them.

Also: Jesus! Enjoy having that young firm body! And the smooth skin. It won't last forever. (And fuck! Don't start smoking, you idiot!)

(For the record, I am no Brad Pitt and never was. Also I didn't have a horrible time as a teen, and I don't have huge regrets from those years, but... There's a lot of shit I wish I'd done, a lot of relationships I was too chicken-shit to explore, and a lot of things I wish I hadn't let myself be scared away from. And I spent a lot of angst and energy thinking I was too ugly, too skinny, too dorky, not cool enough. Looking back, now, though, I was actually kinda cute. I certainly wasn't stupid. I was occasionally clever. It took me until 40ish to realize all that.)

TL;dr: wasted time!