Just ease into it, if you feel your getting crook stop. Only do it for short periods to start, building to longer as you go. Do it at the end of a flight (after circuits or just flying around getting comfortable) so when you start to feel off land straight away. Remember your doing it for fun, when that ceases you should stop. Flying sick or uncomfortable you will not learn anything. Make sure the instructor knows what you want and is the right man for the job. I have had aero instructors who were only interested in showing how good they were, they are there to help you not show off.