What are some anxieties of the GMAT exam? some of these may apply to test taking in general.
1. Got thrown a curve ball on test date. You can practice all your want, but you can't anticipate every situation.
2. You are mixing up your protocol. For example, if you are used to practicing questions by reading them out loud. Obviously in a public testing environment, you will not be allowed to do such an act and disturb others.
3. You can't handle the stress. Period. That's a tough one because that's all mental and you are your own demon. Psyching yourself out.