roller coasters

When supposedly facing fears, we sometimes let ourselves go, blurred within the dizziness of it all. 20 seconds later, when the ride ends, we sort of have to ask if we want to go for another run (swearing this time, it won't be so bad, because we know what we are getting into). Why is it that it still manages to scare the shit out of us every time and make us loose our senses?
So high, so fast, so...