I've been reading John Adams by David McCullough. This an excerpt from a letter sent by John Adams to his son, John Quincy Adams:
Public business, my son, must always be done by somebody. It will be done by somebody or other. If wise men decline it, others will not; if honest men refuse it, others will not. A young man should weigh well his plans. Integrity should be preserved in all events, as essential to his happiness, through every stage of his existence. His first maxim should be to place his honor out of reach of all men. In order to do this he must make it a rule never to become dependent on public employments for subsistence. Let him have a trade, a profession, a farm, a shop, something where he can honestly live, and then he may engage in public affairs, if invited, upon independent principles. My advice to my children is to maintain an independent character.
This quote says a huge mouthful. I can think of very few public servants that come close to this standard.