It is not difficult to find in Saint John’s First Epistle a broad exposition on love from the perspective of our Lord and God. In 4.10-12 we read: This is love: not that we loved God, but that he loved us and sent his Son as an atoning sacrifice for our sins. One’s heart love is not generated from within the individual but is rooted in God himself. Pure love is exemplified in the gift of Jesus for us—and we didn’t earn it at all.
This is the basis for how we are to love each other—with the love which God demonstrated in his giving of his Son for our salvation: Dear friends, since God so loved us, we also ought to love one another. We are called to love each other so completely that we would never base that love on our personal feelings. It just does not matter how I feel about another—what matters is that my heart is set to be Jesus for them.
Simply put, we may be the only evidence God lives to some people: No one has ever seen God; God is the Holy Trinity of Father, Son, and Holy Spirit, and he is not visible to the human eye. It is with the spiritual eye that he becomes evident to us, and that is most often through the lives of others. If one responds to me with the very nature of God’s love for me, that is clear evidence that God is real—and that he loves me.
It is when we love one another that God’s presence is manifest within us: but if we love one another, God lives in us and his love is made complete in us. Then it is the love of God by which we are able to love each other which removes the flesh from the equation. We will never be able to appreciate what love is all about until such time as we fall into the Lord’s love for us. We will then begin to really appreciate God.