I was never sick but I did get VERY frightened during my first flights. Any turn more than 30 degrees would make me scream, much to the instructor's annoyance. Same thing for stalls, I could not stand loosing visual with the horizon.
Less than 100 hours later I now turn 45 and 60 degrees without ever winking an eye. Only looking at the plane's landing gear still tends to make me a bit dizzy.
If you do get in trouble: get as much fresh air as you can, and fix your eyes on one point on the horizon.