What is fear? We don't really know.

We just know it's something we have to overcome some way, someday, somehow.
We know we will go through it, we know we will freak out but in the end... we know we will find out it's not as big of a fear as it was a misunderstanding. We confuse our concepts of extreme excitement and fear, how do we know the feeling we get from heights or while in a roller coaster is fear? Maybe it's just a push that might slip us off to the...