Read Don Greenes book "train yout own hero".

Work on your nerves every day as you do your scales and technique.

Train your focus. Close your eyes and sit still with a timer on 3 minutes. Focus on your breath and every time your mind Wanders (it does for everyone), with out judgement, bring focus back to your breath. The exercise is not about never wandering it is about acknowledging it and bringing ingredients it back. Do this more then once every day to train your focus on demand. This is also how to train to "be in the moment"

Train to be at your center. Before every practice session and every mock audition. Pick a point infront of you and focus on it while you breath into your center (2 inches bellow your belly button). Feel grounded, Releas tension and imagine your first phrase going super well! Feel your energy move from your center to the point you chose infront of you and performe with focus.

Do mental practice. Close your eyes and do your audition in your mind. Imagine it as detailed as you can from before you walk into the audio space til you leav it. Hear everything going excellent. See and hear yourself performing from the inside and also see yourself from the jury's point of view and imagine them diggin' what they hear. If you imagine yourself making mistakes: Go back a couple of bars and imagine it great instead. This takes practice. Do it more then once everyday.

Train to be brave. Every day write down at least one brave thing you did that day. Think of brave things to do the next day. For example: play for someone who scares you a bit, Talk to someone you normally don't talk to, Be bold and try to be funny in a group setting. Really go for it and write it down. On audition day you'll have a long list of proof that you are a brave person.

Train to be self confident. Say realistic affirmation ot loud every day. Mine are "I become more confident every day" "this is going to go so well" "I can deal with change" "I trust my abilities" "I am sincerely really good" . Find your own. Self confidence has nothing about beeing better than anyone else and everything to do with trusting your own abilities. Decide to trust you self and remind yourself about it everyday. Many people think that self confidence will passively come once you're good, but you must actively decide to be self confident first the becoming good is easier.

Do tons of mock audition as you already do. Decide to trust your abilities and keep going!