Plutarch's Rules for the Preservation of Health (12-13)

ZEUXIPPUS. And as the Spartans gave the cook vinegar and salt, and bade him look for the rest in the victim, so in our bodies, the best sauce to whatsoever is brought before us is that our bodies are pure and in health. For any thing that is sweet or costly is so in its own nature and apart from any thing else; but it becomes sweet to the taste only when it is in a body which is delighted with it and which is disposed as nature doth require. But in those bodies which are foul, surfeited, and not pleased with it, it loses its beauty and convenience. Wherefore we need not be concerned whether fish be fresh or bread fine, or whether the bath be warm or your she-friend a beauty; but whether you are not squeamish and foul, whether you are not disturbed and do not feel the dregs of yesterday’s debauch. Otherwise it will be as when some drunken revellers break into a house where they are mourning, bringing neither mirth nor pleasure with them, but increasing the lamentation. So Venus, meats, baths, and wines, in a body that is crazy and out of order, mingled with what is vitiated and corrupted, stir up phlegm and choler, and create great trouble; neither do they bring any pleasure that is answerable to their expectations, or worth either enjoying or speaking of.

ZEUXIPPUS. A diet which is very exact and precisely according to rule puts one’s body both in fear and danger; it hinders the gallantry of our soul itself, makes it suspicious of every thing or of having to do with any thing, no less in pleasures than in labors; so that it dares not undertake any thing boldly and courageously. We ought to do by our body as by the sail of a ship in fair and clear weather: — we must not contract it and draw it in too much, nor be too remiss or negligent about it when we have any suspicion upon us, but give it some allowance and make it pliable (as we have said), and not wait for crudities and diarrhoeas, or heat or drowsiness, by which some, as by messengers and apparitors, are frighted and moderate themselves when a fever is at hand; but we must long beforehand guard against the storm, as if the north wind blew at sea.