There is, however, no advantage in reflections on the past further than may be of service to the present. For the future we must provide by maintaining what the present gives us and redoubling our efforts; it is hereditary to us to win virtue as the fruit of labour, and you must not change the habit, even though you should have a slight advantage in wealth and resources; for it is not right that what was won in want should be lost in plenty.

Book I, 1.123- - History of the Peloponnesian War