The third chapter of Gary Thomas’s Sacred Marriage can be summed up in this quote:
A man who says “I’ve never loved you” is a man who is saying essentially this: “I’ve never acted like a Christian.”
Ouch. Everything about Jesus, the Word, teaches us that our call is to love. We must in all things love God and love others as ourselves – what Scot McKnight calls “The Jesus Creed.” 
And, we would do well to remember that Jesus portrayed His call to love over and over again by loving the least lovable in His society. In our marriages we are simply loving the one we believed we found most lovable at one point in our lives. We may have learned that we didn’t know everything when we believed that, but we are still called to love nonetheless.
Thomas closes the chapter with this:
The beauty of Christianity is in learning to love, and few life situations test that so radically as does a marriage.
Yes, it is difficult to love your spouse. But if you truly want to love God, look right now at the ring on your left hand, commit yourself to exploring anew what that ring represents, and love passionately, crazily, enduringly the fleshly person who put it there.
It just may be one of the most spiritual things you can do.