What was your most chagrining moment?

Hello, guys!

When was your most chagrining moment--when you were brought to utter shame for something that you said or did? And, rather than posit this as another "survey" question--the type you see a lot on this site--I'd like to first present my own example of chagrin:

I was having dinner with my best friend, a dancer who also worked as a waitress at a downtown restaurant--the same eatery where we had agreed to dine. When the time came to leave the tip I fished some change from my pocket and placed it on the table (this was back in the early '80s, where a tip of a dollar or two was still somewhat respectable); when she saw this, she became incensed. As a waitress, the size of the tip was of paramount importance to her, not only as a supplement to her income but also as a way of expressing appreciation for her service. Her face turned beet red and was contorted into a baleful glare as she openly scolded me for my apparent miserliness, and then she said something that came from left field: "I guess it's true what they say, that black people are lousy tippers!" My friend was Jewish and liberal, and up to that moment had never uttered anything that could be construed as being racially pejorative. I stared back at her in shame and disbelief, and said nothing. To this day, the remembrance of that remark still stings

So. What "still stings" for you?