......
Whatever doesn't kill you can only make you stronger. How long were you together? Concentrate on the good times, how happy you were together, and how much she will be missing out by not staying with you. In this, YOU are the number one person. -CAZ- is right - you'll learn a lot about yourself and given time, you'll be able to see things a differnet way. It took me a full 6 months to get over my previous partner (and that was a month of crying, shouting and drinking), but once I finally did and met someone else, it was the best thing that ever happened to me. Now I can look abck and see flaws in the past relationship and tell-tale signs that it wouldn't have worked, and how much better off I am now.
I suggest taking time to do the thinngs YOU want to do, and not doing things you used to do together. Take up a new sport (ultimate frisbee is amazing fun if you can find a team), find a new skill (rock-climbing?), see more of your friends, learn to cook, go for walks, read a book..... you will be enhancing your character, finding new things to apperciate and letting go.
Hope it works out ok