Little shop of horrors audition

Hi all!!
I have a little shop of horrors audition a few months away. I would love to play Audrey, I think I could tackle the role acting wise, but have become very nervous due to her higher notes especially the belt ones in suddenly Seymour. I myself am a mezzo, but have just become so nervous about some of her notes and am almost convincing myself not to audition as I won't be able to hit them if I do get the role. To make matters worse the past week my voice just doesn't seem to be very tuneful. The audition song is probably somewhere thats green which I am more confident with, but I'm already getting nervous about the show and I haven't even auditioned let alone do I know if I will even get it! Any tips on how to improve hitting higher notes which are within your range but are more challenging/ any tips to calm my mind so I can properly prepare for this audition in due time.