I would say "move on", but that's something that you can't control. Just try to divert your thoughts to something else whenever you think about her, and give it time. In time, you will move on.

And don't fall into the "friend zone", girls who know that a guy likes them might take advantage of that and use them emotionally. Like, cry on your shoulder about some guy who dumped her. You don't want that.

I know it's such a horrible thing to say, cos I remember being your age and so in love that it hurt, but you are young - and you will fall for many other girls. It's not the end of the world, even though it feels like it is.
Don't let your feelings get in the way of your friendship. I was deeply in love with my childhood best friend, but he was gay - so it could never be. It was torture being around him, but in time - I moved on.

Btw, are you seeing a psychiatrist? Have you gotten a diagnose? Are you on any medication? I don't know how "normal" people respond to having their heart broken, but I got suicidal every time - thank god the medication I'm on right now is working.
It says in your profile that you suspect that you might be bipolar, if that's the case - you should get a psychiatrist, do the SCID-II test and get diagnosed ASAP and begin treatment. You don't have to live in agony.