I love strolling down the street and seeing a person walking alone, smiling. Not on a cell phone, not listening to a message, not hooked up to headphones, just walking. And smiling. I saw THREE people in a row on the street today in Philadelphia all smiling.  I wondered, what are they thinking about?  Remembering a joke? Heading to meet a loved one? However much I wanted to know, I think it would have been rude to interrupt.