I can't beat Penguin's letter.
Mostly it's just these sorts of things:
1. Be strong and brave.
2. People aren't actually watching you all the time, most of it's in your head. (And what if they are?)
3. You can't have everything. Pick.
4. Better to make the wrong decision and adjust course than not to do anything at all.
5. Life will hurt you but it can't kill you -- at least not in the ways that matter.
6. There is still love in the world.
7. Please PLEASE please invest heavily in Internet stock in 1996. Then cash out by 1998.