Elevated heart beat rate, shallow breathing, eyes wandering from place to place, sinking feeling in your stomack, inability to act and focus.
These are all signs of panic. Especially when you have a deadline coming up soon (public organ performance) and you imagine a worst case scenario (many mistakes and public humiliation).
The worst thing before a deadline is panic.
The one thing you should do is this:
Create a rigorous and realistic practice schedule for yourself and stick to it no matter what. Take action and stop marinating in the feelings you have about the deadline.
Action always eliminates panic.