Everyone feels unhappy sometimes. But it's not a good idea to stay in those bad feelings. If you learn how to keep yourself happy, you'll likely avoid a lot of problems.
Talk to your parents, friends or teachers, and tell them what is going on. It is amazing how much better you feel after talking about your problems.
Do something you enjoy, like reading novels, listening to music, or even sleeping.
Play a sport you enjoy. This will improve your mood.
Keep a "Happy Moments" journal where you write down your best memories, successes, and the moments you felt great. When you feel down, read them and remember how great you are.
Go for a 15-minute run, then take a nice shower, and pick out a new movie to watch!
Do something crazy. Dance in the dark. Scream as loud as you can. Eat a big bowl of something you know you shouldn't.
Think about your goals in life, and how happy you'll be when you complete them.
