[Minishark]

I know exactly what you're going through. Here's a recent example (sorry for the long post, but I'm sort of venting as well):
Last Saturday night I was at a get-together at my friend Tucker's house. It consisted of Tucker's friends (all my friends too), and his stepsister's friends. We were all just sitting around drinking and chatting. One of the stepsister's friends is sitting in the corner quietly, looking a little bored because she's sort of being left out of the conversation (or maybe she just doesn't feel comfortable in big group conversations -- I'm the same way). So I introduce myself to her, and she says her name is Sara. We talk for like an hour. We didn't immediately click, but it wasn't like pulling teeth either. It was a pretty mediocre conversation, I just let her do the talking, asked questions, and said basically nothing myself. She seemed like a pretty smart and pretty nice girl, but nothing really set her apart from the many other girls I've talked to. While we were talking, she didn't act particularly into me, but didn't act not into me either. She was easily the most attractive of the 8 or so girls there, and definitely one of the more attractive girls I've chatted up out of the blue. If I saw her while walking on the sidewalk, I might look twice, but I probably wouldn't remember it 30 minutes later. A few hours later, we're all claiming beds to sleep in, and by sheer happenstance Sara and 2 of her friends end up in the same bed as me, with Sara the closest to me. I have my half of the bed, and they have theirs. I keep my distance; I don't want them thinking I'm some creepy guy that touches girls he just met in their sleep. Every time I wake up in the middle of the night, I notice that Sara has moved closer to me, so I keep moving away, thinking that she's just moving in her sleep and wouldn't want to wake up right on top of me, until I can't move over without falling off the bed. A half an hour or so later, and she's using my shoulder as a pillow. I feel a little uncomfortable, because I'm still not sure if she's doing it on purpose or if she just moves a lot in her sleep. I sit up to check the time, knowing that I need to give a friend a ride home pretty early. When I lay back down, she puts her arm over me, looks up into my eyes, and starts kissing me. Needless to say, I was surprised. Here's a girl who I'd barely even talked to for a hour, and she was making out with me. Normally when this happens, the girl is either (1) drunk, (2) crazy, or (3) ugly. This girl was none of the above. The time rolls around when I need to drive my friend home, so put my number in her phone, and go. Now, normally I would get the girls number, but like I said, this girl was pretty nice, pretty good-looking, but nothing spectacular. If she wants to call me and hang out, fine, but I'm not going to spend my entire summer vacation chasing this girl, because I didn't feel that into her. That was how I felt then.
Now, a few days later. She hasn't called me, and I can't stop thinking about her. I barely even remember what she looks like, but now I think she's the most beautiful girl I've ever seen. I talked to her for barely an hour, but now I keep thinking about how well we'd get along if we were together. It seems crazy that I feel attached to her now, even though when I was with her I felt nothing.

So anyways, the point of the story is that it's really easy to let your imagination run wild when you meet somebody new. Since you barely know them, you fill in the blanks, building them up in your mind to be this perfect person, and then you just drive yourself crazy. Even before you've really gotten to know them, you've already psyched yourself out, and now you're so intimidated by your own fake mental image of them that there's no way you could ever be comfortable around them. You've already essentially blown it for yourself before you've even begun. I believe the technical term is "putting the *************** on a pedestal".