Plutarch De capienda ex inimicis utilitate 10

[10] But since as Simonides ¹ puts it, and since all human nature bears its crop of contention, jealousy, and envy, as Pindar ² says, a man would profit in no moderate degree by venting these emotions upon his enemies, and turning the course of such discharges, ³ so to speak, as far away as possible from his associates ⁴ and relatives. This fact, as it seems, a statesman, Demus by name,e apprehended: when he found himself on the winning side in a civic strife in Chios, he advised his party associates not to banish all their opponents, but to leave some of them behind, in order, he said, that we may not begin to quarrel ⁵ with our friends, through being completely rid of our enemies. So also in our own case, if our emotions of this sort are expended upon our enemies, they will cause less annoyance to our friends. For a potter must not envy potter, nor a minstrel a minstrel, as Hesiod ⁶ puts it, nor must there be any feeling of rivalry against a neighbour or relative or brother who is winning his way towards riches and meeting with prosperity. But if there is no other way of getting rid of strifes, envies, and contentions, accustom yourself to feel the sting of resentment when your enemies enjoy health and happiness, and whet your contentiousness to a sharp jagged edge on these. For just as skilled gardeners believe that they improve their roses and violets by planting beside them garlic and onions (since whatever pungency and malod rousness there is in what the plants feed on is all drawn off into the vegetables), thus also your enemy, by taking up and diverting to himself your malice and jealousy, will render you more kindly and less disagreeable to your friends in their prosperity. For this reason it is with our enemies that we must also engage in rivalry for repute or office or honest money-getting, not only feeling the sting of resentment if they get the advantage of us, but also watching carefully every means by which they get the advantage, and trying to surpass them in painstaking, diligence, selfcontrol, and self-criticism: after the manner of Themistocles, who said that Miltiades’ victory at Marathon would not let him sleep. ⁷ For he who thinks that it is by mere good luck that his enemy surpasses him in public offices, in pleading cases, in state administration, or in his standing with friends and leading men, and who from activity and emulation sinks down into a state of utter jealousy and discouragement, has abiding with him an envy that is inert and ineffectual. If, however, a man is not blind ⁸ in regard to the object of his hatred, but makes himself an honest observer of the other’s life, character, words, and deeds, he will discover that most of the successes which excite the envy of others come to those who have won them as the result of painstaking, forethought, and fair conduct, and so, bending all his energies in this direction, he will put into practice his own ambitions and high aspirations, and will eradicate his listlessness and indolence.