When we surrender our lives to God through Jesus Christ and we are born again, God’s nature, which is love is imparted to us through the transforming power and presence of the Holy Spirit. Why do you suppose that God commands us to do something like love one another and our enemies if it is our nature to do so? I think it is because as D. L. Moody put it, we leak. We can be distracted by things that can cause us to drift away and lose His holy presence by grieving the Holy Spirit. The commands to love help to keep us on track, and if we have drifted, to repent and get on track again.