Lol. I always try to be polite when I'm out in public. Someone holds the door, I tell them thank you, you know, whatever. But sometimes something happens different from the hum drum normal routine.
I always tell people they don't have to be polite to me a work, it's my job. And then when someone doesn't say thank you I still catch myself almost saying "you're welcome". :P
I go to the same store everyday. I always make a purchase with my debit card. The same cashier always asks if I want my receipt. I always answer, "No, thank you."; Today I was ready. I made my purchase using my debit card. The cashier told me to have a nice day. I answered, "No, thank you." And walked out the door.