Prepare properly in a timely fashion, and nerves, uncertainty, and frustration can be avoided. The key to confidence, is preparation.
Embarking on an audition, jury, or performance can be very stressful, for the amateur and the elitist. The difference between those who progress and those who fall behind is the methodical practice done beforehand. The knowledge and skills gained from this type of work will yield confidence, leading to a successful performance.
Knowledgable practice and a healthy level of confidence will diminish fears, leaving you with the joy of musical satisfaction.