We ought to give our friend ...

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.
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.

Quotes from the same author

Silence at the proper season is wisdom, and better than any speech.
Know how to listen, and you will profit even from those who talk badly.
To make no mistakes is not in the power of man; but from their errors and mistakes the wise and good learn wisdom for the future.
I don't need a friend who changes when I change and who nods when I nod; my shadow does that much better.
What we achieve inwardly will change outer reality.