Hello LuckyIcecube

I am not entirely sure what exactly could be causing this - but I found a blog here on PsychCentral that does mention this in an Anxiety blog -

"Stress anxiety is caused by a clearly identifiable event and fades as soon as the crisis is over. (Amusement parks make a great deal of their money by provoking this kind of anxiety. The jolt in your stomach when you speed down a roller coaster or when something jumps out at you is the fight-or-flight response in action. The rush of adrenaline feels so good, you want to take another ride.)"

http://psychcentral.com/lib/understa...art-one/000297