"Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy. 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; That ye may be children of your Father which is in heaven: for he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust." Matthew 5:43-44.
Oh, how the flesh drives us to wanting. The flesh has its own motivations, its own desires, its own ways: steering us toward sin. The flesh desperately seeks the path of least resistance, in order to preserve its dying husk. For the unbeliever, there is absolutely no chance of resistance, because the unbeliever is dead in their sin, and trespasses: blinded by the darkness. The way of the wicked is as darkness: they know not at what they stumble. Proverbs 4:19. Foolish, disobedient, lead astray, hated by others and hating one another: this is the way of the dead, in which we all walked. For the Christian, for the one who has been born again of water and the Spirit, there is hope, and it is found in the Way: it is found in Jesus - in whom is life and the light of men.
Jesus leads the Christian, to see reality, in light of eternity. Since all have fallen short, including every person who calls themselves a "Christian," we - as Christians - are able to empathize with the lost, remembering our lost condition, and knowing the reality of the heavenly dwelling which awaits those who are in Christ, and the stark juxtaposition of the outer darkness which awaits those who have rejected the one Way to life, that God has provided, through Jesus Christ.
The Christian can love his enemy, because he was once an enemy of God, in his mind. Yet, God, knowing full well that the Word of His power could completely obliterate those resistant of His will, gave a peace offering to His enemies. "...but God shows his love for us in that while we were still sinners, Christ died for us." Romans 5:8. Loving your enemy is something that God did, first, and the demonstration of this love was through what was accomplished on the cross, in the atonement for the sin of the world, by the blood of Jesus Christ.
This is how we love our enemy: we remember that God accomplished this first! The Lord told us:
"A new commandment I give to you, that you love one another: just as I have loved you, you also are to love one another." John 13:34
This cannot be accomplished by the flesh, but only through the power of the Spirit of Christ! It is a merciful, self sacrificial, humble and meek love, demonstrated by Jesus.