well first you have to acknowledge why she broke up with you, then if It's fixable, work at it! if the relationship is done then no matter how hard it is, its done. if your young and try moving on she may come back, but don't count on that. you been to keep moving because the world will not wait for you. see the roads ahead and know there is a bright light, there are so many people in this world your going to meet, don't be discouraged. get out there! be yourself and have fun for now. life will work its way out correctly. be smart and happy. ok? and know what you got and what she is missing out on.
Move on. Forget about her. You can't dwell on the past. You have to forget about it, and focus on the future. Move on to the future. It will usually be hard to move on, but you have to stay strong no matter what and move forward. Flirt with a bunch of other girls, do things with friends, do something you really enjoy, hang out with your family, do anything that will keep your mind off her. If it doesn't work, try to remember any mean things she said/did to you. Find a reason to hate her for.
it's gonna be okay. I know it can be hard to move on at times, but friends are there to help you through it. Try flirting, but don't rebound girls...they hate that. everything happens for a reason, i guess.