Eh, come on, surely you got something out of it, had some decent times right? Better to dwell on what you gained (and learned) than what you didn't - after all, you're not really worse off than you were before (though I'm well aware how your emotions are going to attempt to adamantly prove the contrary).
Most of us have been there, found someone great only to have it all go to pot for one reason or another, usually when things were looking their most promising.
Fuck dude, I once gave a girl my berries, my super special berries, my lemons, my limes - we spent the evening together, we barely wanted to leave at the end... and then she refused to even speak to me afterwards, god knows why! Talk about ungrateful - you'd think that would at least earn a verbal "no I don't ever want to see or speak to you again" rather that absolute radio silence. Especially since her roommates were incredibly cool and I was looking forward to seeing them again almost as much as the girl. Bluh, I say!
But in the end, you know what? It was a damned good evening (and the time leading up to it), I had a great time with someone I liked (at the time), and I was better off than if I'd ended up doing a host of other things.
Obviously you're going to have to kick your emotions in the nuts to even TRY to think like that, but even if you don't succeed 100% I usually find it to at least be worth the effort.
Edit:
Also, lying to myself helps! Clearly she fell for me so fast that she scared herself off due to her fear of commitment.
Or desired for commitment she didn't think I could provide (for pretty good reason).
Or maybe she just couldn't handle my incredible brain and amazing body, thought it was too good for her.
Either way. Doesn't have to actually be TRUE, that's why it's a lie!
(Not actually sure I recommend this last bit)