Letter 1567: A teacher must live what he teaches.

To Theodosius the Presbyter. That to bear insults and injustices brings glory here and will bring the greatest renown hereafter, I know very well. But that to feel gratitude toward the one who wrongs and insults you — as toward one who drives you to a greater philosophy, especially when he does this repeatedly and even boasts of it (not to mention that I would wish my crowns to be woven from others' misfortunes) — this is the greatest thing, and beyond my own power. I can bear being insulted and wronged, but I have not yet achieved the ability to feel grateful to those who wrong me, and to pray sincerely and ardently for those who constantly harass me — especially when they do not even wish to repent, but even laugh at those who pray for them. Learn this from me: if you yourself have achieved even this, I greatly praise and applaud your magnanimity. For I myself — I shall not conceal my own shortcoming — having often prayed purely for those who have treated me badly, have sometimes found the prayer difficult to sustain with complete sincerity.