I had a very unusual experience on a flight to CLT last year.

At some point during our mildly bumpy landing approach a decision was made not to land but to go around and try again. I have no idea why, and it doesn't matter. It seemed like a normal situation and really didn't bother me in the slightest. I just kept on reading my book. There was a little more turbulence as we circled back.

For some reason my body reacted with some sort of very strong stress response. I broke into a sweat and felt pretty ill. I thought I was going to need help getting off the plane, but I was near the front and managed to stagger into the terminal and, close to fainting, found a washroom. I sat in a stall for a few minutes until my body composed itself and eventually went on my way.