Being from the south and raised in a military family you're pretty much taught to be polite, unfortunately not everyone adheres to that. That being said I would say that I am very polite. I say things like 'yes ma'am' or 'no sir' and even 'thank you', even if it's not expected of me. Like someone else said, if I'm in a depressed mood I may not always adhere to the rules of politeness as it were, but it definitely isn't personal.