I have come to realize that whenever a student says, "I can play it perfectly at home," they aren't realizing that they really couldn't play it perfectly at home. It is just that during their practice time they aren't paying attention as much as they do in the lesson, so what I tell them is practice for perfection.
...probably very similar to what a student experiences when playing for an audience of one after playing alone all week.PC
The point I was trying to make, however, is that if as an adult student you can remove the concept that you are playing for an audience or performing, and enter the idea that you are both working on a project which is what and how you are playing, then that anxiety disappears. Mistakes are almost a welcome thing, because they become opportunities. It's like being on your hands and knees putting a jigsaw puzzle together - no stress.
After reading this thread, I have determined to be more honest with myself and my teacher. Last week, he asked me what I had acheived in practice - rather than a more ambiguous question of "How was parctice". This put the lesson in a positive place to begin with. I have asked for help in places that I can't get the feel for. I have tried to listen to the piano instead of perform. Lessons have been useful. It is important as an adult to be a partner in the process and to have soem idea of what I need and want to learn.