In your case the Hypnosis will implant suggestions in your mind to help you find calm in times of anxiety. Anxiety and stress are learned responses to stimulation. When you learn to refocus these feelings into productive energy, you feel much better.
When going for a session. Go with curiosity. Know that it can't harm you because your mind wouldn't allow it.(The doctor can not make you cluck like a chicken unless you want to.) Make sure you are well rested and avoid caffiene just before your session.