-Don't wish you were older. Responsibility is big deal, not necessarily a happy deal.
-Do everything you can. Go to singing classes, karate, diving, fencing, dancing....anything in the world you can find. You'll only be this brave and uninhibited when you're ten, at twenty it'll halve and and at thirty it'll seem silly. Oh, and you won't have time for it.
-Homework is not the worst thing that can happen to you. There are bigger and worse things you'll need to face, and no, I'm not talking about a zit.
-Enjoy your time with your parents. Your parents are young when you're ten. Play with them, ask them a million questions and exhaust them! They'll only get older as you get older and their time with you will keep getting more and more limited.
-Don't be in a rush to fall in love. Spend as much time with yourself as you can. There is a time for loving another person and when that time comes, you'll find there is lesser time and love you can give to yourself.
-There is a different freedom at every age- make sure you enjoy it.
-Wisdom comes at a price, enjoy your innocence.
-Whatever you do, as you get older, keep fighting cynical people. Happiness is yours to claim.
-Don't ever stop imagining or being curious.
-TV is evil. Go out and play hop scotch.
-Eat as much as you can, your metabolism will suck when you're older!
Oh and quick PS to my 35 year old self:
Don't wish you were 25 again. At 25 you wanted to be 15 and at 15 you wanted to be 25. Shut up and enjoy yourself.