Here is a GREAT video from Kiko Loureiro (Lead Guitarist) and Dirk Verbeuren (Drummer) of MEGADETH.
Kiko and Dirk, two of my favourite musicians, not only for their incredible skills, but for their amazing positivity! In the video they discuss how they practice and prepare themselves to play in front of an audience.
I believe their music advice is appropriate for Photographers:
We too must practice until using our equipment becomes second nature. We must practice so we do not look foolish when performing in front of clients! We must practice so our photography gigs run as smoothly as possible, and IF we are prepared, we have fun instead of being stressed out about performing our job — preparedness leads to confidence, and that is also a BIG DEAL for Photographers!