I just got off the phone with a lady from JCPenney. I have an interview tomorrow at 2 pm for a seasonal sales associate position. Situations like this just make me so anxious. It took me forever to work up the nerve to even call her back. I really need to go to this interview but I'm afraid I'll bail because I'm too nervous

This is very important to me. I currently live at home with my parents, broke and with way too much time on my hands. I need a job desperately.

Does anyone have any tips? How do I remain calm before/during the interview?