A meme from many.
5 things you would tell your 16-year-old self if you could:
1. Spend as much quality time with your parents as possible.
2. Take care of yourself now, because later it's going to be harder to do so.
3. When you get to college, make sure you stay off the internet.
4. Don't listen to others when they put you down, because it means they have insecurities
5. You ARE worth it!
BTW, now that I've filled these out, I don't believe I would do anything to change my past. Had I changed my past I'd never end up in the life I have today, and really, I'm pretty damned happy in the life I have.