Just a few hours ago - while driving, the person next to me gave me a quick verbal correction and the natural response of "Thank you," came out.

Now, technically, I don't think that should count, so I'm also gonna throw in that I send a thank-you note to someone, no matter what the occasion, every month. It's a good habit to get into, because you're always reminded of the kindness of others. You keep up the handwriting, and the etiquette of writing a letter. Don't let the past generation die.