I have this theory, that as soon as people are presented with what they claim they want most, they run away. Then again maybe it's not everyone, maybe it's me and a few people I've observed. The person who wants to make more friends yet turns down opportunities to hang out with new people. The dude who wants to get a date but runs away if someone shows interest (even if he happens to be interested as well).
I guess it's fear based; fear of success, fear of failure, they are almost the same thing, or at least they seem to make people behave in similar ways. Of course, sometimes it isn't just an opportunity that knocks, but more or less exactly what you wanted that jumps into your lap, and indeed it was invited, by you.
I have no remedy for this as of now.