I don't like lifts and will walk up 20 flights of stairs if I have to. Crowded rooms make me uncomfortable, too, although I can sing to a stadium full of thousands of people no bother.
For me, it started as a child with one of those little wooden jigsaw maps of the U.S., where's there's crocodiles on Florida and apples on Washington state. That was my very first map.
The funny thing is most people don't approach me because they are scared, and that's fine, I want to keep it that way. But the thing is if you're not scared or get over it you learn that sometimes what you're scared of is really what you shouldn't be scared of.