I started out in gliders and had no problems with heights then. As a child and a teenager I had a normal fear of heights but this didn't translate into a fear of flying. I then started flying a flexwing microlight. This had just a fairing around my feet and a lap belt. I quickly got over any fear of height but ever since, I have had an opposite affliction; the urge to jump out.
I'm a perfectly sane individual with no mental health issues and enjoy life immensely, but when presented with a big drop, a large part of me wants to jump. What makes this particularly odd is that I've never been attracted to skydiving. It goes away though in enclosed cockpits and high-sided open cockpits. Perhaps I should skydive just to scratch the itch.
I've flown aeros, both powered and in gliders and found that the only new fear factor to get over was when hanging in the straps whilst diving near vertically under negative G. It took about 1/2hr to get over it and now I can't wait until I have the pennies to buy into a Christen Eagle syndicate.
If there's anyone out there who wants a very willing victim for the front seat of their Extra/Pitts/Eagle/Cap then please let me know.