Well, you have enemies. Indeed, who could live on this earth without them?--St. Augustine, Commentary on the Lord's Sermon on the Mount: With Seventeen Related Sermons (Catholic University of America Press, 2001), 252-53
See to it that you love them.
In no way can a raging enemy injure you as much as you injure yourself when you do not love your enemy. He can damage your farm or your flock; he can injure your household--your manservant or maidservant, your son or your wife, or, at most, he can injure your body if he has been given the power. But--unlike you--can he injure the soul?
Dearly beloved, strive toward this perfection, I exhort you.
Is it I that gave you this? It has been given to you by Him to whom you say: 'Thy will be done on earth, as it is in heaven.' And do not think it impossible, for I know that there are Christians who love their enemies. I know this, for I have discovered it and proved it. You will not even try to love your enemy if you think it impossible for you to love him. Therefore, begin by believing it possible, and then pray the will of God be done in you. If your enemy had no wickedness, he would not be an enemy. But, how profitable his wickedness can be for you!
. . . You are still saying: 'Who can do it, and who has ever done it?' May God do it in your hearts. Very few do it, I know. Those who do it are noble and spiritual.