How can I improve my auditioning skills?

So, I had an audition today on clarinet. (It was actually a challenge against a person to move up a chair). Long story short, I failed so badly, I cannot even attempt to convey to you how badly I messed up on the stuff that I had been practicing for weeks.

I don’t think I completed a single octave of a single scale correctly, even though I’ve known several of them for five years. I hyperventilated and my hands were shaking so badly I could hardly turn a music page (and I had some nausea). I messed up my etude pretty badly even though I received it over a year ago and have already auditioned multiple times with it. I pretty much forfeited the challenge without actually forfeiting the challenge.

So, I am in some desperate need of some advice to improve my auditioning skills lack of ability. What do you recommend?