My advice:
I used to be terrified of heights. I wouldn't ride drop towers or tall coasters either. Then, I went into Boston and went to the top of the Hancock Tower (which is maybe about 700-800 feet tall) and I got very close to the window. I looked down, realized that it was stable, and just like that I was over it.
It's kinda like if you get punched in the same spot over and over again, it doesn't hurt after a while.