First off, stay in school! No matter how much you hate it, no matter how much you're made fun of, Graduate. It's the smartest thing you could ever do.
Next, when the older guy makes a comment about your baseball jersey, keep walking. And get Kim to keep walking too. I know, I know, Kim can make her on choices, but that older guy, he started what would turn out to be ten years of hell, with the occasional heaven thrown in.
In case Kim should happen to hook up with Gary, try not to fall in love with his best friend. Have a fling with him, if you must. But for goodness sakes don't fall in love.
Stop defying your mother. She loves you very much and just wants to keep you safe. And tell daddy he's special too. After all you're his little girl, no matter how old you get.
Keep talking to Genna. No matter what distances come between you. You only have so much time with her before you have to say good bye. Make sure you get that chance. Don't let what you think is love keep you from your friends. Don't shut everyone out.
You're not crazy. You're just ... a little unwell. Nothing to be ashamed of. Don't be afraid to ask for help. Don't keep your thoughts and feelings locked away. You've got enough crap going on in your head.
Start writing again. You have so many ideas, good ones too. If you get them down on paper, you'll be thankful.
Last but no least, if you don't follow my advice, have no regrets for the life that you've lived. Learn from mistakes. Learn from others. Learn that no one is perfect and you will be loved for who you are, not what you can give to people.
With much love and no regrets,
Lala (one day I'll explain that to you)