We ought to give our friend pain if it will benefit him, but not to the extent of breaking off our friendship; but just as we make use of some biting medicine that will save and preserve the life of the patient. And so the friend, like a musician, in bringing about an improvement to what is good and expedient, sometimes slackens the chords, sometimes tightens them, and is often pleasant, but always useful.
PlutarchThe new king [Alexander the Great] should perform acts so important and glorious as would make the poets and musicians of future ages labour and sweat to describe and celebrate him.
Plutarch