Study carefully, ahead of time. If you cram' at the last minute, you're likely to end up very tense. Avoid your significant other before the test. You may be frazzled and upset. Don't talk to others before the test.
Anxiety is easy to spread.
If you are not anxious already, you might become so. Relax during the test. Some tension is normal and can help you focus and do well, so accept it. These exercises can help keep the tension at an acceptable level. Take several slow, deep breaths.