I was once in the checkout lane at the local grocery store, and felt someone pushing me in the behind with a grocery cart.
I had had a bad day, so I was somewhat annoyed. So I spun around a bit angrily, to chide the person behind me. No sooner did the words, “Excuse me! Are you bl-—!” start to come out of my mouth, that I noticed that he was wearing dark glasses and carrying a white cane.
Boy, was I embarrassed.