What can i do to make sure i get the best score i am capable of on the test?

i have my biochemistry final in exactly 2 hours. I have studied over 40 hours in the past week. I have gotten an A and a B on the previous midterms. however i am freaking out that i will screw it up and get an F and end up getting a C in the cl. i always feel like this on finals and i actually end up doing pretty bad