There are two personal pitfalls that I run across regularly in my professional life: desperation and disappointment.
I see a lot of actors who are desperate to get that next job and then disappointed when it doesn't come through. It's a vicious circle and it's fed by one thing: exaggerated expectations.
I get it - I've been that guy. OH GOD HAVE I BEEN THAT GUY! The anxiety, the craving, the obsessive spinning of "What If's?" It's easy to fall into and it's not productive.
But lately I've adopted a philosophy to cope with that:
"It is what it is."
Hey, that next gig MIGHT be the one that changes your life. But you know what? You are not making the decision. You don't even know who else they are seeing. All you can do is walk in, do your best, smile, and walk out.
If you succumb to the anxiety, not only are you giving away the little power you have over your performance and your presence, but you're also demonstrating how weak and unprofessional you are.
And then when you don't book the gig, there's all the coping with the frustration and disappointment. Unless that produces some sort of performance insight or redoubled motivation, it's wasted emotion.
An audition is not a job. It is what it is: two minutes for you to be the best you can be for that part. And then it's over. It doesn't owe you anything and you have no obligation to invest any more time or energy into it. (Unless there's something to note or learn for a callback or future auditions.)
Manage your expectations. Control what you can. Live in the situation at hand and don't go off in the head-trip of what-if.
Anxious actors look desperate and green. People want to hire people who are grounded and competent. (Sure, they'll put up with a lot of shit from celebrities if they have to, but I guarantee you those people are PRAYING that celebs will be competent and grounded on the job.)
Don't let your emotions get the best of you by letting your expectations outstrip the present reality. It is what it is. No more, no less.
-Tom, who notes: If this was preachy and boring for your non-actor people out there go back and substitute the word 'audition' with 'date'.