Fear of Rollercoasters

I have a huge fear of rollercoasters! everytime i'm on one i feel the tense and my heart pounds so hard and so fast that i could hardly breathe when i go on something high! i always make the same face and i cant stop it.

i also cant scream on a really fast or high ride. Either its me or my fear but i just want to know how to get rid of it before i go to a theme park.