I show courtesy to everyone I meet.

An older man counts coins onto the counter, slowly, with a queue behind him. The assistant waits without sighing and without the little performance of patience that is worse than impatience.

Courtesy is the form kindness takes when you've run out of warmth.

It's shallower than affection and available on days when affection isn't — you can be perfectly courteous to somebody while privately wishing they'd move faster. That isn't hypocrisy. It's the minimum civil floor that lets strangers share a space, and it does more work in an ordinary day than the grander feelings do.