Nasty business that vertigo thing. I suffered it for a while as a child, then I jumped off our kitchen roof with an umbrella and realised that I could get a handle on this issue. The dreams are worse, I often just fall asleep and find myself falling from a tall building. Wonder what causes it?
Yeah, it may be that the experience itself makes you more used to the fear. But when you are asleep, you don't have the same faculties of sense (or memory) that you have when you are awake. That might lead to more scary experiences.
I hear you, falling off a building in your sleep will make you shit yourself.