How do you get over nervousness before you tryout for something?

Question:

How do you get over nervousness before you tryout for something?

I sing and whenever I audition for something, I crack and I try to be confident, but it still doesn't work. Can you please give me some advice in detail?

Additional Details

3 days ago
I sing and always audition for things. I am currently in a highly advanced choir at my school but I still audition for other things. But no matter how hard I try to believe in myself or no matter how confident I am, I crack. I do practice as much as I can but somehow it doesn't work. I have also asked help from my director which has told me to keep working. I need more advice though.

Best Answer - Chosen by Asker: 3 days ago
I sing and always audition for things. I am currently in a highly advanced choir at my school but I still audition for other things. But no matter how hard I try to believe in myself or no matter how confident I am, I crack. I do practice as much as I can but somehow it doesn't work. I have also asked help from my director which has told me to keep working. I need more advice though.