It's completely normal to "freak out" after an audition: Did I do good? Did they like me? Shoot I missed up on this line! No one laughed! etc. etc.
The truth is - you will never really know what the other side of the table is thinking. So the most important thing is to work on your acting and your attitude.
Rehearse rehearse rehearse.
Get as much time as you can in front of the camera - even if that means mock auditions with your friends/classmates. This will help you to get start getting comfortable in high pressure situations, like your big auditions.
DON'T MISS CLASS.
In class, we're working on camera, almost every night. This is PRACTICE FOR YOU.
And with your attitude.. you gotta show up, do your very best, and leave it at that.