Eat sunflower seeds - they are a natural anti-depressant... and Magnesium calms people down.
ooh suplemnts like what ??
You could also take a couple of supplements especially for anxiety: gelsemium or Sepia.
Great advice from tarheel78.
But also do a lot of preparatory work. I found practicing on old exam papers under exam condition (timing myself) helped me.
If you go through and revise you will be equipped and ready.
Before you go into the exam room, make sure you go to the toilet to empty yourself (nerves can make you want to wee more).
In the exam room, shake your hands at the side of your body, roll your shoulders and take a deep breath. This will help you to relax your body.
When they tell you that you can begin the test, Do not forget to read the paper for instructions first. And turn each page so that you do not miss out a question.
My daughter forgot to turn a page and missed out a whole question. Luckily she still did well with the other questions and passed.
Best wishes and hope you do well.
Exercise, Listen to music, play sports, go running, relax with friends, good rest, and healthy eating.