Hi madgmat2019,
To help manage your nerves, you could try some visualization techniques. Imagine various test-day scenarios such as getting stuck on a question, issues in the testing center, feeling pressed for time, or worrying that you’re underperforming. As you feel your stress responses start to kick in when thinking about these things, practice pulling yourself together and visualize focusing on getting correct answers.
When taking the GMAT, the best way to deal with stress is to get busy answering the question in front of you, focusing completely on the task at hand so that you redirect all of that nervous energy and naturally calm down. In other words, you distract yourself with a goal. Just tell yourself that all that matters is getting the correct answer to the question in front of you, and then when you have finished that question, take the same attitude toward the next one. Focus on winning each “mini-battle” and you won't have time for anxiety. If you can win enough of those battles, you can win the GMAT war, right?
I wrote an article that provides some more detailed advice about
how to limit GMAT anxiety.
Please reach out with any further questions.