This is interesting, because I have been actually thinking about this very question lately...
I have noticed that throughout my life, I have been extremely shy and hesitant to get involved with people. I might flirt, and then feel rather embarrassed about it, and happy at the same time, if that makes any sense? If I end up getting to know someone, I have a range of inward experiences. They are basically inicial attraction where I end up thinking along similar lines as what randomsomeone wrote, and then the point of no return, where I either commit myself to either giving it a try, or giving it up entirely. (where I end up creating an ideal beginning or ending for the situation).
When I have truly committed, it has still entailed a degree of repulsion at some point along the way. I can recall a moment during my last long term relationship, where he began to stay the night at my home, and I had some mixed feelings about it getting even that far. I remember looking at his face while he slept, and discovering all the silly little physical and character things that for whatever reason bothered me somehow, and I felt very stressed about the fact that I was actually committed to this person. I then remember thinking to myself, that I would just have to allow them to grow on me, as well as just ignoring the confusion that I felt, due to the fact that they had never bothered me previous to the commitment. After some time of just getting used to this new person in my life (and that took a great deal of time and effort on my introverted part), I found myself trying to fight feelings that were quite the opposite of the repulsion that I had previously gone through. I was fighting the "falling in love" part. That was (and generally is), more frightening to me than the fear of maybe not being able to fall in love.
At this point, then yes, I am doomed, completely devoted and also a child, following the old music man... Sigh...