Polite people do get burned out and tired of serving others, but still keep good grace around them. They can still have those feelings, but they might choose to repress it for a later time. We aren't all nice ans polite to each other, maybe because they don't feel understood, or are saying something that they would rather not say aloud, if you get my drift. I don't think it is because of the sinful nature. Everyone is rash at some point.
