tobster911
Anxiety is a very well known phenomenon and every pilot has at least heard about fellow pilots who once had problems in that region and overcame them. I've seen people who just didn't like the acceleration, be it negative or positive, in the beginning, just kept on flying and never again had any problems, and others who took professional advice that eventually did the trick for them.
The previous posters have already mentioned very much depends on the level of your discomfort. Please bear in mind you can always get professional help from aeromedical personnel or your instructors.
What helped me to become reasonably indifferent towards small negative Gs is some piece of advice I remember having once picked up from an interview with an aerobatics pilot. I think it might have been Patty Wagstaff, but I'm not sure. The advice was to keep your abdominal muscles relaxed and not try to work against the negative Gs. Most of us will remember from our childhood days how much we enjoyed swinging. The magnitude of negative acceleration on a swing is comparable to what you encounter during non-aerobatic flight. From this comparison you will see negative Gs do not hurt, they didn't when we were children on a swing and they do not hurt in an aircraft either.