If you want in on the fun, just post a letter to yourself on your blog and add your name to this list. If you're participating, here's the code to add the below linky list to your site. And don't forget to check out all the other letters.
And now, for my Dear Teen Me letter!
Dear Girl with Big Hair:
Yes, you think you look cool with all that Aqua Net in your permed hair...
Okay, scratch that. You don't think you look cool. Not at all. In fact, you're pretty sure you have the chubbiest cheeks of anyone in the whole world.
You'll grow out of those. You'll also find that what you read in Seventeen magazine is correct--people with round faces look younger longer. That will all change once you hit your 40s, but enjoy looking younger than you are while it lasts!
Also--YOU AREN'T FAT! You look great. The older you get, the more you'll puzzle over the fact that you don't see that. (The hair looks ridiculous, but that's just because it went out of style sometime not long after that picture was taken of you.)
Enjoy college. Stop worrying about guys. Have fun with your friends and learn as much as possible because you'll spend the rest of your life working.
(Oh...and, by the way, you might want to pay particular attention in English class. Writing skills will be more important to you than you realize!)