Mental preparation involves having a certain frame of mind. Ask yourself what are you thinking about. Worrying about making mistakes or having people criticize you can cause anxiety. Spiritual preparation was referred to as including emotional stability, self-confidence, and a sense of inspiration. Finding out who you are and how you're going to express yourself is essential.
Motivation can contribute to performance anxiety.
Even in a competition, for example, if the performer is trying to do his or her best rather than trying to be the best trumpet player in the competition, there is likely to be less anxiety. Closely related to motivation is purpose. Music is a method of communication, and if you really feel the message and the trumpet is a true extension of yourself, that message can be communicated to the audience. The audience will remember the message, not the mistakes. As performers, we tend to worry about the notes, intonation, technique, etc.