1) “The one knowing what is profitable, and not the man knowing many things, is wise.” — Aeschylus
2) “It is with our passions as it is with fire and water, they are good servants, but bad masters.” — Aesop
3) “Men of sense often learn from their enemies. It is from their foes, not their friends, that cities learn the lesson of building high walls and ships of war.” — Aristophanes
4) “The wise man does not expose himself needlessly to danger, since there are few things for which he cares sufficiently; but he is willing, in great crises, to give even his life – knowing that under certain conditions it is not worthwhile to live.” — Aristotle