Ever since I was 8, I could crawl on any roof, just about any pitch . . . as long as I was at least 5' from any edge. As long as I had that buffer - I was good. But anytime I had to get close to the edge - that lizard part of my brain could already feel that sickening, floating feeling as I would go off of the roof. Also have problems with rollercoasters, being at the window in a skyscraper - or even seeing it on TV.