*Sees topic is about self-esteem*
Guess I'm late to the party.
Basically, Chrissie and Jerk both got it down pat, but I can add some of my own personal experience.
Frankly, if you have low self-esteem, you're not going to put yourself out there. And if you're not going to put yourself out there, you're likely to be ignored and your self-esteem will plummet further. It's a vicious cycle.
As some of you know, I nearly had a break down once because being alone started to bother me (A LOT), so I had to make a decision: Ask out this girl I know has an interest in me, despite the fact that I never thought I had anything to offer her, or just stay alone.
I finally did, and it was the fucking hardest thing to do.
Regardless of what happened afterwards, she said yes (though I'm still kind of grinding my teeth about how she had to force it out me. What? I'm a lazy bastard. You should know that.)
You wouldn't believe what that can do for you, to know that someone else thinks more highly of you than you do of yourself. Makes you think 'Hey, maybe I'm not such a bad person after all.'
And once you have that mindset, looking down on yourself is going to start looking more and more like a stupid idea. I don't think I'll ever get rid of my self-image issues, but as a guy who has benefited from thinking that I might not be such a bad person to hang around with, I can say that the more you start focusing on how worthless you aren't and more on what you have that other people might not have, the easier it will be not to fall into that same trap cycle again (just don't become an arrogant ass in the process, m'kay?)
Also, I too feel slightly guilty for going on looks, but only because I feel that I should really get to know a person before I try anything (before, I was way too cautious), but being attracted is just what us humans do, and sometimes you just need to tell yourself that over and over so that you won't have that big a hang up about it.
...I totally forgot where I was going with this, so I hope you got something out of this.
EDIT: @MDL: Yeah, if you want Chrissie to want you more, you're going to have to stay out of reach for a while. Because when she finally catches you, she'll be all the more desperate.