St. Bernard on The Four Loves

ON THE LOVE OF GOD
Why God Should Be Loved - You ask me,  Why should God be loved??
I answer: the reason for loving God is God himself. And why should God be loved for his own sake? Simply because no one could be more justly loved than God, no one deserves our love more. Some may question if God deserves our love or if they might have something to gain by loving him. The answer to both questions is yes, but I find no other worthy reason for loving him except himself.God is entitled to our love. Why? Because he gave himself for us despite the fact that we are so undeserving. What better could he have given? If we ask why God is entitled to our love, we should answer, Because he first loved us. God is clearly deserving of our love especially if we consider who he is that loves us, who we are that he loves, and how much he loves us.
And who is God? Is he not the one to whom every spirit bears witness: "Thou art my God." God has no need of our worldly possessions. True love is precisely this: that it does not seek its own interests. And how much does he love us? He so loved the world that he gave his only Son; he laid down his life for us.
The First Degree of Love: Love of Self for Self's Sake
Love is a natural human affection. It comes from God. Hence the first and greatest commandment is, "Thou shalt love the Lord thy God." But human nature is weak and therefore compelled to love itself and serve itself first. In the human realm people love themselves for their own sake. This is planted within us for who ever hated his own self?
The Second Degree of Love: Love of God for Self's Sake 
God, therefore, who makes everything that is good, makes himself to be loved. He does it as follows: first, God blesses us with his protection. When we live free from trouble we are happy, but in our pride we may conclude that we are responsible for our security. Then, when we suffer some calamity, some storm in our lives, we turn to God and ask his help, calling upon him in times of trouble. This is how we who only love ourselves first begin to love God. We will begin to love God even if it is for our own sake. We love God because we have learned that we can do all things through him, and without him we can do nothing.
The Third Degree of Love: Love of God for God's Sake
In the first degree of love we love ourselves for our own sake. In the second degree of love we love God for our own sake, chiefly because he has provided for us and rescued us. But if trials and tribulations continue to come upon us, every time God brings us through, even if our hearts were made of stone, we will begin to be softened because of the grace of the Rescuer. Thus, we begin to love God not merely for our own sakes, but for himself.
The Fourth Degree of Love: Love of Self for God's Sake
Blessed are we who experience the fourth degree of love wherein we love ourselves for God's sake. Such experiences are rare and come only for a moment. In a manner of speaking, we lose ourselves as though we did not exist, utterly unconscious of ourselves and emptied of ourselves.If for even a moment we experience this kind of love, we will then know the pain of having to return to this world and its obligations as we are recalled from the state of contemplation. In turning back to ourselves we will feel as if we are suffering as we return into the mortal state in which we were called to live.
Can We Attain the Fourth Degree of Love?I am not certain that the fourth degree of love in which we love ourselves only for the sake of God may be perfectly attained in this life. But, when it does happen, we will experience the joy of the Lord and be forgetful of ourselves in a wonderful way. We are, for those moments, one mind and one spirit with God.I am of the opinion that this is what the prophet meant when he said: "I will enter into the power of the Lord: O Lord I will be mindful of Thy justice alone." He felt, certainly, that when he entered into the spiritual powers of the Lord he would have laid aside self and his whole being would, in the spirit, be mindful of the justice of the Lord alone.
St. Bernard of Clairvaux
For more on St. Bernard's life and writings see: http://www.crossroadsinitiative.com/library_author/69/St._Bernard_of_Clairvaux.html