Fear of heights in all its forms is, I believe, the 2d most common
phobia (the first is fear of speaking in public, officially, but I'm guessing more people confront heights than the need to speak in public so I'm guessing heights might be the most common fear). I have this phobia, but didn't have it until I got a full-blown anxiety disorder. If this is your only phobia, good; if you have several and are anxious about a lot of things, harder.