It seems also that all instructors seem pretty immune, so my guess is that this is something that you get used to and the ill feeling reduces.
tdbristol,
Well, I was exactly the same as you, but I got over it as well. Now, I'm an instructor who is allegedly 'immune' Yes, I can do 4 or five 1-hour flights in pretty bumpy conditions with only feeling really tired at the end of the day, but because I remember what it was like for me at the beginning, I hope I'm sympathetic and encouraging to those who suffer.
Oddly enough, I did come back from a trial leson in fairly bumpy conditions a while back (though not nearly as bad as last Sunday, we cancelled our whole programme) feeling a bit queasy. Another instructor confided in me that he'd felt a bit rough on the same day, too, so we're not all completely immune. However, having the responsibilty of someone else to look after does take your mind off it.
TheOddOne