Wow, you sound like me when I was younger
I'll tell you two stories.

1:
For a few years, my entire world revolved around this girl. Thinking about her constantly, one-sidedly and unrequitedly planning an imaginary future together, etc. She was absolutely NOT interested in me at all, and this completely crushed me. We both moved, and the distance helped, but not entirely. What finally did it for me was that she did something that really offended me to my core, and made me unable to even remotely consider her as "dateable". (No, I'm not going to tell you what it is, but I will say that yes I realize that was very judgmental of me, and yes I've cooled off considerably since then.) Although in reality...while I was no longer attracted to her, then I had to deal with the problem of my fictional ideal of who I wanted her to be getting destroyed. Sorry, thought it'd be a lot more helpful when I started typing it.

2:
Another girl. This one actually went out with me, for more than a year. And then left me. Like in the previous story, we both moved away, but as it happened, I moved to the city where her parents lived, and she moved to the city where my parents lived. No contact for two years. But, then for the next two years, we would see each other every 3-6 months - for instance we had lunch when she came to visit her family, and we had coffee when I went to visit mine, etc. We were both seeing other people at the time, weren't at all interested in each other, but there was still awkwardness. Anyway, long story short, I had to go on a trip, didn't want to go alone, asked a lot of people to come with me, and she was the only one who had the time/money to do so, and for some reason agreed. It's amazing what three weeks on the other side of the globe can do...engagement ring a few months later, been married 5 years now.

As an epilogue, I bumped into the girl from story #1 at a mutual friend's wedding last summer. We made a little chit-chat, and it was pleasant enough. I emailed her the next week to say it was nice seeing you, but she didn't respond. I'd like to be her friend again, but it doesn't look like that's in the cards, and I can accept that now with no problems whatsoever.
(chase, Thu 8 May 2008, 18:06, Reply)