Welcome to soaring! Sounds like you went up on a day high time pilots
would call fun. Don't worry, most students or passengers, would be sick
by the time you got off tow. What you probably experienced was a feeling
of loss of control. The fact that you recognized that you were getting
airsick and ask to come down before you threw up, is a good sign.
Lots of (daredevil types) pilots get airsick when learning to fly. When
the instructor has to take control in these conditions, you lose
confidence in your ability to control the glider. All you learned in
rough air, is that you are not ready to handle the conditions. No
different than a beginning mountain biker on a trail way over his head.
Lucky for you, the instructor can take over when you loose control in a
glider. The instructor has a tendency to expose you to rougher conditions
than he would a meeker student. The fear you experience is no different
than when you started down a narley MTB trail the first time.
Primary instruction (at least in the beginning phase) should occur in
mild conditions. Arrive at the airport early in the day or later when
conditions are calmer. As, your lessons progress, you will learn that you
can handle the conditions and remain in control of the glider. Don,t worry
about thermaling or or staying up in rough conditions yet. Lots of high
time pilot got sick early on. Myself, I was airsick in 15 minutes, for
about the first 10 lessons. As I progressed, the airsickness slowly went
away. By the way, I have been flying and mountain biking for 30 years, and
neither is boring.

Ed Gaddy, Cycle Logic Bicycle Shop