St Jerome's comment on the portion, "Love your enemies," I find to be quite striking. With a knife, he cuts away that part of us which would have us believe that we've done well not to hate our enemies. He also then directs us to true love--concluding with Our Lord's love for us in His prayer.
The Lord hath said unto us: Love your enemies; do good to them that hate you. Many there be who measure God's commandments by their own weakness, and not by the strength of his Saints; and so deem him to have commanded things impossible. Of such are they who think that the best they can do is not to hate their enemies; and that to command us to love them, is to command more than man's nature can bear. It behoveth them to know that Christ did not command to do what is impossible, but what is perfect. On this wise it was that David did, in respect to Saul and Absalom. And likewise, the Martyr Stephen prayed for his enemies, even while they were stoning him. And even so Paul could wish that himself, and not his persecutors, were accursed from Christ. On such wise Jesus both taught and did, when he said: Father, forgive them, for they know not what they do. (Source)