I used to say that I was content with not really having a big social life. I was wrong.
I think I'm kind of the same way. I've never really been a social butterfly, nor have I been able to maintain good, close friendships with people, but it never really bothered me in the past. However, that was when I was still in school and still participated in some extracurricular activities -- I was interacting with people regularly, and even if I wasn't especially close with anyone, I got along quite well with most of my acquaintances, and I could have fun with them.
Now, school's done. I haven't done any major extracurricular activity in a while. Sometimes, I go days without any real human contact (today for example, unless you want to include the girl at the grocery store cash register). I used to say, "Yes, I may be alone, but that doesn't mean I'm lonely." Well, I don't think I completely believe that anymore. Most of the time, I can find something to occupy my thoughts with, but I have to admit, occasionally, I get a little lonely. And that can be frustrating.
As for infatuation, I think I know where you're coming from
Drone. I've never had a serious romantic relationship, and much like with my friendships, that hasn't bothered me too much in the past. Heck, truth be told, although I've met plenty of girls whose company I enjoy greatly, and plenty I've been very attracted to (and yes, occasionally these two groups overlap), it is very rare that I actually meet someone with whom I want to pursue a relationship. I don't know why, but the whole idea of being in a committed relationship never really appealed to me.
From about the time I was 14 to when I was 24, I had maybe a couple of semi-crushes on people. That was it. Then a couple years ago, I met a girl. Adorable. Smart. Good sense of humour. Fun to be around. Shared some common interests with me (not
Trek though -- at least I don't think so. Ah well, nobody's perfect.

). I developed a crush on her instantly. Over the next year, I saw her sporadically, but enough for my feelings for her to intensify -- yes, I think I actually developed real, true feelings for her; up til then, to be perfectly honest, I wasn't sure if I was capable of having strong feelings for someone in that way. I wouldn't go so far as to say I was in love with her, but... it's the closest I've ever come.
So naturally, she was unavailable. She has a boyfriend, and from what I can tell, is very happy with him. While I of course don't begrudge them their happiness, it did naturally make my infatuation all the more unpleasant. It almost made me wish I could go back to being the cold, unfeeling bastard I used to be.

So yeah, I think I know how you feel
Drone. All those years of feeling like romantic attachments were unnecessary, and then BAM -- it hits me when I least expect it. It probably would have been easier if I hadn't experienced those feelings, but, as has been said in this thread, we're not Vulcans, so what can you do?
As for the girl in question, I've only seen her a few times this past year. Not being near her seems to help a bit, but when I do see her again...

I can't help but still be rather taken with her.
On the plus side, though, knowing that I am capable of such emotions is kind of nice. Perhaps I'll experience them again someday, and perhaps next time, the circumstances will be more favourable (true, knowing my luck, the next girl I fall for will probably also be taken, but hey, a man can dream

). So I guess that's one way of focusing on the positive in such situations; I hope you'll be able to find some way of doing the same.