Sex, emotional fulfillment,take your pick.
However, YOU need to decide if you can't handle the ups and downs, and if you can't, you need to cut her off. Not saying you can't eventually one day be friends or whatever, but now is too soon. You need time to adjust to the fact that you aren't going to be together, and nothing tends to betray that fact more (in a person's mind, usually) than still being allowed to stick your penis in her.
So, I'd back off and tell her to give you some space.
[SIGPIC]http://img409.imageshack.us/img409/2509/glyphmb9.jpg[/SIGPIC]