I encountered, this summer, a teacher who made me think: If I had to study under this individual, I'd likely quit the martial arts. That has never happened before. I don't know what this says about me, but I do know what this says about the way this sensei taught. His skills were excellent, but he was belittling and arrogant. He made you feel your attempts were insufficient even when you were trying your best. And although it was all done under the guise of jest, it was still enough to impact the lesson in a negative way.
It takes a lot for me to say something this strong, but the truth is, that I wouldn't want to learn from someone who cares so little for the feelings of his or her students.
Maybe this is a poor attitude on my part, but it makes me appreciate the other teachers and fellow students I have encountered along the way.