St. Seraphim of Sarov: On Preserving Spiritual Peace

It is necessary to strive to preserve one's spiritual peace by any means possible. Do not be upset by the insults of others. Strive in every possible way to restrain yourself from anger and to guard attentively both your heart and mind against unbefitting emotions.
Therefore tolerate the insults of others with equanimity and try to preserve your disposition as if these were not directed at you. Such and exercise will bring peace to your heart and prepare it as an abode for God Himself.
We see an example of such forbearance in the life of St. Gregory the Wonderworker, when a certain prostitute publicly demanded that he compensate her for an alleged sinful encounter with her. He, not becoming in the least angry, meekly told his friend to give her the money she was demanding. The woman had no sooner taken the money than she fell subject to an attack of a demon. Then the holy one prayed and drove the demon from her.
If on the other hand, you find it impossible not to become offended, then at least you should try to hold your tongue, for as the Psalmist said, "I was troubled and did not speak."(Psalms 77:4)
+St. Seraphim of Sarov, from Spiritual Instructions, On Preserving Spiritual Peace, in The Joy of the Holy.