In my case at least the fear was worse than the actual thing. Since childhood I've always been afraid of heights but only if I am close to an edge. e.g. can't stand next to a cliff, or a low-ledge balcony etc.
But since then over the years I've flown a Cessna, climbed a climbing wall and even went skydiving.
My lesson was that the fear was the worst part. The actual experience was quite enjoyable.
My next goal is a roller coaster! ;-)
PS. I still have a phobia of being upside down. Stall and spin training seems scary as hell and I am not sure if I can ever manage an acrobatic plane in my life!!