Moreover, when I recalled what dangers I had undergone on behalf of these people even in my earlier advocacy, I decided that the credit of my earlier service must be preserved with a new favor. Indeed, there is a general consensus that you undermine earlier benefits unless you compound them with additional ones, for however often people have been in debt to you, once you refuse them some one thing, they remember that thing alone that has been denied to them. [ancient testimony to the paradox of rising expectations]

source: Pliny the Younger, Letters, 3.4.7 tags: Service, Expectations