It is different for everyone.
I get sweaty and my heart goes about 100 beats a second.
But that really does not effect my shot.
In my opinion a couple deep breaths is worth a lot when the
moment of truth comes.
When you target practice get up close to the target and close your eyes while shooting.
Doing this every once in a while will help you not worrying about rushing your shot and
will help with being "Trigger Happy" .