History of the Peloponnesian War

And if any one think that he shall certainly gain some advantage, either by right or might, let him not be annoyed by failure through the unexpected result; knowing that many men ere now, both while pursuing with vengeance those who have wronged them, and hoping, in other instances, to win an advantage by greater power, in the one case, so far from avenging themselves, have not even saved themselves; and in the other, instead of gaining more, have happened also to lose what they had.

For vengeance is not necessarily successful, because a man is injured; nor is strength sure, because it is sanguine. But the incalculable nature of the future prevails to the greatest possible degree; and though the most. deceptive of all things, still proves the most useful: for because we are equally afraid, we are more cautious in attacking one another.