I got sick on my trial flying lesson too, and nearly gave up... but gave it another try, and felt fine on the second one. I got my Private Pilot's Licence in 1989, and I still fly.

I don't think motion sickness is something you can ever overcome totally - but you can certainly build up a lot of resistance to it. I still get seasick. I sometimes get sick in the back of the car. Sometimes I even get sick when I look at moving pictures shot with an unsteady hand (i.e., amateur video). I have been known to get sick when flying as a passenger in a light aircraft. But flying myself I am usually fine.

I was fortunate in that I had very understanding instructors, who were able to help me build my resistance. In the early days they made sure I only flew on calm days. Gradually I started flying on days that were less calm. Sometimes lessons had to be cut short because I started feeling a bit queasy, but as time went on this happened less and less.

If I were you I'd give it another try. Pick a calm day. Make sure the instructor is aware of your predicament. If, after two or three lessons, you still find that you get airsick then maybe it isn't for you. But I wouldn't give up just yet.