When I got off the A train this evening, someone waved to me. I didn't recognize him--just a random middle-aged white guy--but my habit is to return any greeting unless I have a specific reason not to, so I waved back.

At that point, he said "How are you doing?"

I recognized the voice. It was someone I specifically didn't want to speak to, so I just walked away. But I'd noticed that, well, that he wasn't looking well, in a tired/drawn way, and that he'd changed enough that I didn't recognize him at first.