Why do we think we love God when we do not love our neighbor? If we do not love what God has made, how can we love the Maker? When we fail to love the image of God which we can see, we cannot love the Ground of all Being which is unseen.
The way to love the Invisible One is by loving the visible. St. Augustine explains that we were given the second greatest commandment so we would know how to keep The Greatest Commandment. If we cannot keep the second, how shall we hope to keep the First?
We learn to love God by loving others. Love your brothers and sisters around you whether they are young or old, rich or poor. Love them all the same, no matter the color of their skin. Yes, they may think differently than you. They may have done you some injury. That does not matter. Remember: our Lord was crucified by those who thought differently than him yet his very death was the proof of his love for them—yes, for them.
Love others and you will love Jesus. What you do for others, you do for God. This is the way of the Good Shepherd and we are His sheep.