St. Ambrose of Milan.
+ + +
If I despise, hate anybody, it signifies that I unlawfully exalt,unlawfully love myself - that is, my flesh. Our heart continually,flatters us, secretly exalting ourselves and depreciating others. But we must constantly see our innumerable sins in order to judge ourselves, to weep over ourselves, as for the spiritually dead. Then we shall not have time to notice the faults of others, and to condemn our neigbors for them, or to despise them; but we shall esteem them, for we shall find that they are incomparably better than us in many things.
When you see men fall into various sins against yourself, against the Lord, against their neighbors, and against themselves, do not be angry with them - for there is much anger and malice in the world without your anger - but pity them from all your soul and excuse them when they offend you, saying to yourself: "Father! forgive them," for sin perplexes them; "they know not what they do" (St Luke XXIII, 34.).
Saint John of Kronstadt
+ + +
"But as soon as the spirit has begun to love heavenly things, as soon as it has bound itself with all its intention to the vision of inward peace, the old adversary who fell from Heaven is envious and begins the more to lie in ambush. He imposes harder temptations than was his wont, in or order often, thus, to tempt the resisting spirit as he had never tried it before when he possessed it. Thus it is written: "Son when thou comest to the service of God, stand in justice and in fear, and prepare thy soul for temptation" (Eccles 2:1)."
St. Gregory the Great
[The Homilies of St. Gregory the Great On the Book of the Prophet Ezekiel]