Thanks to my nephew Dan for getting me on this track. The link in not obvious. In 1969 I walked into my first real class of 90 students as a full time teacher. I had spent the better part of 10 years in college preparing and had studied on the cutting edge of many areas of biology. Still, I knew in my bones that I was unprepared and just one question away from being revealed as a fraud. Throughout my full time teaching career which spanned nearly 40 years the fear of discovery was never far below the surface. "If they only know how little I really know......"
This phenomenon is called the "fraud hypothesis" and is present in almost everyone at some level. Research over the years indicates that many people perceive themselves as barely prepared for the task and "If only I had a little more time I could get really ready." Seems to be a normal human trait. The reality is that "they" don't care how little or how much you know as long as you know what they want or need to know and can guide their learning it.
I had a professor in college many years ago who was also my mentor and friend. I once told him that I had let both of us down by not doing enough. He told me that when we evaluate ourselves we factor in all the things we know we didn't do, or did badly, or repeated to get right, but when someone else does it they only see the outcome. And he was pleased with the outcome. Basically he told me to get over it and get on with it. I did. Sort of.
Years later when I taught my first anatomy and physiology class I thought "God, if they only knew how little I really know about this they would walk." I had prepared exhaustively for every concept and knew as much as was humanly possible, but still, but still someone might figure out the fraud. Once again I pulled it off.
Another thing this wise man taught me was to say "I don't know" when you don't. My students will affirm that I do that regularly. Hey, you can't know everything, and if you think you do, you really are a fraud.