I'm not sure that there will ever be a clear cut answer to your question, everybody handles things so different. If you're completely 100% positive that it's over between you and her then the one thing you can do as bad as it hurts is just make sure you're dealing with how you really feel and working through it. Let yourself hurt for a little while. I don't necessarily think it's healthy to try and jump right into another relationship until you are sure you're ready for one. It's not really fair to the person you might be jumping into it with also, not to mention yourself. For me as petty as it sounds too, if I try to remember why we ended it in the first. I try to focus on reasons that we aren't together and things that I found fault with with the other person. Sometimes when a relationship ends and you still have feelings for the other person you may try to romanticize the relationship, only remembering the good times you had with the person instead of seeing the relationship the way it truly was. I hope this maybe helps you a little bit, I'm sorry you're in that place at all. It's a tough spot to be in.