1. When you feel unhappy, don't push those feelings away. That just makes them last longer. Let yourself feel totally unhappy, cry it out, etc, and then afterwards you'll feel much better.
2. If someone does something that makes you unhappy, be honest with them. Pretending you're ok just makes you more unhappy.
3. Don't rely on other people to make you happy. In order to be happy, you have to say, "okay, I am happy with what I have. I don't need anything else."
4. BE YOURSELF. Don't try to be different in order to make other people like you. You'll be really unhappy even if you do get them to like you, because you won't be able to be yourself. Say what you really think, how you really feel, who you really are, and the right people will appreciate you for that.
5. Don't ever feel like there's something wrong with you. You're beautiful the way you are.