About seven years ago, on my daily commute, I passed a woman from my neighborhood walking her dog. As our paths crossed on the sidewalk, I smiled and said, "hello." She glared at me and said nothing. I figured that she was just having a bad day, and let it pass—until the next day, when the same thing happened. I smiled and said hello.  She glared at me and said nothing. 

Shocked and a little miffed by her obvious lack of common courtesy, I carried that glare and the self-righteousness it inspired within me most of the day...