If you are determined enough you can overcome it. I was medically suspended from RAF FJ training because of airsickness. I could just about cope with the Jet Provost at 400 knots and 6g but I needed 3 hands to fly the (550 knots/8g) Hawk. One each for stick, throttle and blue bag. I was given the desensitisation course at Farnborough but didn't help my case by hurling all over the station commander at Honnington in a Hunter T7 whilst holding prior to the course.....Very sorry Group Captain Shaw!
I "talked" my way into a multi engine course and am now flying commercially in LHS of B767. Its 23 years since I started flying and I still feel very ill when paxing, and trying to read a book in a car or coach is guaranteed chunder time. However, its now rare for me to feel anything more than mild discomfort when operating and, if really necessary, the first class superloo is a joy to throw up in!