Breakups are hard to deal with, its just one of the facts of life. What you experience is mostly the same whether you are an adult or a teen. This article discusses some advice for teens dealing with breakups.
Do not take it personnel when someone leaves you, it may have nothing to do with you. It could be that the two of you did not match or that things just did not work out. The other person probably cares about you but did not want a relationship. Do not take rejection too serious, a lot of people break up that care about each other but are not interested in having a relationship.
If you are thinking about talking trash about your ex or taking revenge of some kind, put it out of your mind. This would be a bad idea because this will make you look bad and any good feeling you may derive from it will be short lived and people may think of you in a bad way. Don't hold a grudge against the other person, you will only hurt yourself because of the anger you hold inside, let it go.
You will have some bad days after you break up with some emotional times to get past. You can cry, get mad and feel hurt inside, these are all normal reactions to breaking up. Do not take your feelings out on your ex, talk to your friends or family to let go of these feelings.
Everything may look terrible now but who knows what the future may bring you. You may meet another person that is perfect for you that you would have missed otherwise. Maybe you and your ex will cross paths again and then the time might be right for a relationship.