When I was a very small kid (~3 1/2), I stepped onto the top tread of a two-story escalator in a huge downtown Cleveland department store, tripped, and fell.
Since I was just a toddler, and dressed in a snowsuit (we'd gone to Sterling-Lindner's to see Santa Claus), I didn't get hurt. But I was frightened and crying, and never liked
heights after that. Like many people, it wasn't the elevation that scared me, it was being close to the edge with nothing to grab if I started to go over. I gradually got over most
of my fear, but it took a lot of clenched teeth and mentally kicking myself in the ass to climb a ladder or stand on a balcony.
Then, when I was seventeen, I was painting dormers on a 3-story house, lost my footing, and slid on the slate roof almost to the edge. Had to start all over with getting over the
fear of falling. Glass elevators gave me the creeps, and 12-story atriums in high-rise hotels had me hugging the walls on the way to my room. Again, it wasn't the height per se, it
was the fearing of having nothing to grab with my hands if I lost my balance.
Flying has never bothered me, and one of my greatest pleasures has always been flying in open-cockpit planes. But a visit to the Grand Canyon actually had me crawling on all fours to
look over the edge, with my hands trying to clench finger-holds into the ground I was on.
I finally realized that most of my anxiety had to do with not trusting my balance and reflexes. When I worked at Wright-Patt, there was a parcourse right behind my office, which had some of those
2" wide balance beams about six inches off the ground. I started walking those every day, slowly at first, then faster, and in high winds, and even backwards. The more I practiced, the more
relaxed and confident I became. I realized that no matter if it was six inches off the ground, or six feet, or sixty feet, the process was exactly the same. This helped a LOT, as well as forcing myself to
go out onto high balconies or precipices, relax, and simply stand there without moving for 10 or 15 minutes.
I'm fine now with ladders and scaffolds, and with high overlooks –– as long as there's no smartass who thinks it's funny to shove you or pull you off balance. (Almost got into a serious punch-up over that
several years ago.) I think identifying the exact cause(s) of your fear is important, and work through it incrementally. Build trust in yourself. I've heard that hypnosis can help, but never tried it.
The only thing that still gets my heart rate up momentarily now, is getting onto the first step of a 'down' escalator. I still hesitate for a split second, grab the handrail firmly, and THEN step on.