Some people get very nervous when they perform. I'm one of them. My hands usually sweat a little, and often shake. My stomach churns. Two hours before the performance, I start asking myself why the heck I ever decided to play publicly, especially for all my students and their parents.
I used to worry about this, but one of my graduate-level piano professors set me straight. Dr. Kirchberger once told me, in his rich German accent, "I only had one student who never got nervous before he performed. He was a complete idiot."
It's probably true that almost all normal, non-idiots get nervous prior to a performance. That thought can be comforting.