I've found that post break-up, it's best if you treat the situation as though your ex has died; it makes it much easier. Because, it's like, sad, but you have no choice but to move on.
Come to think of it, if you stick to that story, it would probably actually help in picking up the next girl...you know, if you tell her your ex died...because of the sympathy points, and all. (They had a Seinfeld episode where, after George's fiance dies from licking poisonous wedding invitation envelopes, Jerry does some research with the waitresses at the local diner and they agree that being a widower is the sexiest break-up story.) Although, if things end up working out with the new girl, your entire relationship will have been predicated on a lie. But, if movies have taught us anything, it's that you can say whatever you want to get the girl in the first place, and as long as she falls in love with you, all you have to do is apologize for aforementioned lies and she'll stick around; just say you lied because she was so pretty, or something.
Jump to the 7:45 mark to see the Seinfeld clip I was talking about: