Quandary

Why is it, that groups sometimes put on their best shows or pieces in rehearsal? Last night, IA had a great longform piece. It was a beautiful thing to be a part of, and I couldn't do it any justice explaining it here. I just want to know what others think about rehearsing something great without anyone seeing it. Sure, we learned a lot from it, and we hope that we outdo ourselves in a show with people watching. But it sure seems like we always do great stuff when no one is around, is it just me?