"Now let me get something straight: you are not in my debt. You can't be. Impossible-because I never do anything I don't want to do. Nor does anyone, but in my case I am always aware of it. So please don't invent a debt that does not exist, or before you know it you will be trying to feel gratitude-and that is the treacherous first step downward to complete moral degradation."
~from Stranger in a Strange Land by Robert A. Heinlein