Just try to move past it. There are tons of other girls out there, I was with a girl and really messed it up and was pretty pissed at myself. The best way to get over it was listening to music and reflecting on what messed it up. I have found someone twice as nice. Just try to push it out of your mind with other things, you'll never forget her that we know but just use a picture of her as some rolling paper or something, sure it'll taste like shit but it'll still be a cool way to end it all.