If you're more relaxed you'll perform better. Plus, if you enter an exam in a positive and relaxed mind set you'll go in, see the question, and start writing fluently and everything you've read and wrote over the past 2-5 weeks will come out.
Those who are stressing the fuck out right now, studying till 4am and getting up at 8am to study all do everyday and are drinking redbulls and caffeine etc are more than likely to burn out in the exam or have too much information and then they will panic and most likely hyperventilate, and spend more time calming themselves then answering the question. It's like, they have ruptured a pattern of consistent sleep and activity for 2 weeks, thus their brain is not working normally.
So, reiterating, you will perform a lot better than them - EVEN CONSIDERING YOU HAVENT STUDIED AS MUCH - because your brain is still working in a way which it has become accustomed to for 13 years of academic institutionalisation and you are positive that you know you will do well.
...but yeah, I'm not stressed.