I have talked with fighters who have had the same problem. Some tried relaxation techniques, meditation, yoga, etc: Some work cross word puzzles or go to a movio before a fight. And some, tell me they work themselves into a state of rage before a fight and focus on nothing but winning. Which one is correct....I honestly can't say. What works for one, does not work for another. Like a writer before me, I think the more fights you take on and the more confidence you build within yourself will solve the problem. If you mind can conceive the thought that you are a good fighter, you can make it happen.