Yeah dude been there, done that. What can I say? It sucks balls. I'm not sure how in love with this chick you were or how many relationships you've been in that were this serious, but life will go on! The sun will rise tomorrow the same as it always does.
The best thing I can say to do is to accept it and move on, then cut off all communication, at least for a while. It will suck not talking to her or seeing her, but it's the best thing for you to help you get completely over it. I could go on and on here but in general you need to be very active and social.
Go to the gym, hang out with buddies, your family, whoever and whatever--just stay busy. Any down or alone time will inevitably be spent thinking about her, causing you to get sad and depressed.
I've also been in a bad rut before and the best thing you can do to counter that rut is to do whatever is necessary to get out of it. If you're in debt, create a budget and set up payment plans. If you're out of shape, work out. Consider going back to school to take some more classes or something, learn a new skill...keep busy and active and always be improving yourself!