It might be to your advantage to play your audition before groups of people; family, friends, fellow band members. And do it regularly.
You might benefit from a very basic book called "The Relaxation Response". I've done various meditation and self-realisation exercises for decades and I think that book is still one of the best ones going for people who just need a basic, non-esoteric and easy to understand and learn process of relaxing at the drop of a hat. In moments of high stress just before (or even during a performance), I can drop my anxiety level greatly and instantly just by saying three simple words from this book's process. Check it out.
Probably the greatest lesson I have learned in taking stress out of performances and keeping focus, is to take my ego out of it. Of course, a pop cover band gig in a club is not the same as a solo performance before an attentive audience, so they're not all the same. But when it's required, taking the ego out of it means two things. From a playing point of view, it's having what I call a "don't give a ****" attitude. Basically, that means you play what you play and you can't give a damn what comes out. It's hard to put into words, because obviously, you do give a damn, but it's the difference between being brave and timid.
The other is looking on yourself, not as the focus of attention, but merely as a conduit. That is, you are not the center of attention of the music, the music flows through you. The music exists "out there" someplace, you (and your accompanist/band etc) bring it into life, and it flows through and out to the listener. When I think of myself as part of a continuous flow, and remove my ego from the process, I tend to make fewer mistakes.
One last word. I practically never get "stage fright" but I have had it come out of nowhere, uncontrollably. I have performed on television and before dignitaries and been cold as steel, and yet, I've turned around and gotten a bad case of shakes before simple community functions. Rarely, but it's happened. That's why I have developed the above tools to back me up.
Oh - I don't know if it was mentioned above or not (apologies if it was), but before these auditions or performances, get a good night's sleep and eat well. Have your morning planned well and avoid last-minute panics.
p.s. I just went to Amazon to check on "The Relaxation Response" and one of the reviews said that there is a revised version that has a lot of medical data at the expense of some of the original text. Anyone interested in getting this book should probably be aware that there are original and revised versions, one of which might be better for them than the other. (I cannot say. My comments are based on the original.)