I have seen that the more exams and tests you give, the less fear you have of them. Thats because once you practice giving so many exams, there is less uncertainty about the format of a paper and its questions.
Generally, I never think of how much my exam is worth, etc - that just makes me more tense. I do my best and let the rest happen.
A little bit of fear is actually good to have - it pumps you up and sends an ardelanine rush. This may help you write well. But, too much fright is not good; you should not blank out.