Moving on to the second part of the mental game that I covered:
B. The audition itself - how do you achieve the most focused mental state that will allow you to show your best stuff.
This is somewhat more difficult than the first part we covered. The first part of mental preparation takes place before the audition, and you don't have to feel any outside pressure (i.e. adjudicators staring down your tonsils while you sing!). You can do mental preparation in the quiet of your practice room or bedroom.
Achieving the mental focus and calm that you need during an audition is trickier because you are attempting to, in some ways, trick yourself, into having the right type of mental focus and energy. Nonetheless, I think it's doable!!
When I was "coming up" the stock answer to "how do I make my self less self conscious, and more confident in an audition?" was - Picture the auditioners in their underwear!! Well, maybe it's because I'm the auditioner now, but I think there are better ways to get your mind focused in the right way during an audition!
First, the assumption here is that you are completely prepared for the audition under consideration - technique, memorization, dramatic intent and execution, all must be there - if you are nervous because any one of these is not ready, no mental trickery will fix the problem, and you probably shouldn't be in the audition in the first place.
Assuming all of your ducks are in a row, I think the key to having the right mental focus during your audition comes down to one word - intent. What is your intention during this audition? Start with communication - text and character - moving your listener. Since you can only control what leaves you, and not how it is received (and this is of course true in any circumstance), this can free you up considerably. A general director or other person in a position to hire you, or give you money, is really just another version of your Aunt Jinny, who might be just as hard on you or harder as any GD anyway!!
Humor aside, the point is, you can't control others perceptions of what you do, and wasting mental energy on worrying about it will undoubtedly detract from what you do.
When you sing the Habanera, only worry about being Carmen and focus on what you as that character are thinking and being. This will create a successful audition for you. You getting hired or winning $10,000 was never in your hands anyway, so concentrate on being successful on your terms.