But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you. If you do, you will be perfect, even as God is perfect.
How can we be perfect?
Father Jonathan explains that the true meaning of that term is probably closer to "finished" or "mature, fully aged, complete" than to the English definition of "without flaw". In other words, as you mature in your Christianity, you will begin to love your enemy out of a realization that it is the most mature and responsible thing you can do for yourself. It's the best reaction. It works.
These are far and away the most difficult concepts for some of us Christians to accept. In fact, some contend that Christianity is a religion of cowards, teaching submission and weakness. A shallow interpretation.
And these are certainly the most difficult imperatives for many of us to live. But if you don't do this difficult work, your Christianity is not mature, fully-aged and complete, (and you are not living the joyful and free life that Jesus wants for you).