One of the biggest temptations of academic life is the desire to play it safe. Professors are in the unique position of setting the agenda, delivering the goods, and assessing the outcome -- all on our own. If we don't want there to be a moment of truth for ourselves, there doesn't have to be one. We're little gods in our classrooms. We say what needs to be learned, then we measure whether it is learned, and we equate that process with actually mastering a discipline that is larger than ourselves.
That's why I like pushing myself to have moments of truth as an instructor. What it takes is breaking down the classroom walls enough so that somebody other than myself has a view of how I'm doing. Often that means outsiders are seeing how my students are doing, judging my teaching by their performance.
The moment of truth is frightening, no question about it. You have no control over the forces in the real world that are going to impinge on your work. They might be merely physical, like the effect of a washing machine on a garment; they might be malevolent, like Internet trolls. But until you put it out there, you'll never know if your work can stand up under the pressure. The reason we professors hate being vulnerable is the same as the reason we should embrace our moments of truth. They are the measure of our worth. Do we want to know, or don't we?