During my first quarter in high school, I heard a few students asking teachers for their quarter grade estimates up to that point. I asked my high school orchestra director, Mr. D., for an estimated grade, thinking he'd say something like, "Don't worry about it. The way you play, you've got an A." Instead, he replied,"A minus...A minus to B plus. What's with this vibrato you've got?" Mr. D. was referring to my unorthodox left hand position when doing vibrato and tendency to use it only sparingly.
Despite my unorthodox approach to vibrato, I got an A in orchestra that quarter and every other quarter. I got the message, though; even if you play well, don't coast and take your A grade for granted.