"We got quite off the beaten path, but I seem to remember you being upset with me when you called. Did I do something to offend you?" Well, crap. How do I complain about that? "No. Not anymore. I'm good." "But if you don't tell me, I'll never know, and I'm liable to make the same mistakes over and over, never learning my valuable lesson. You're a teacher, correct? Please help me learn."