In spite of ourselves, something is kept back. It is not that we are untrue in this, and hide our inner self, but simply that we are unable to reveal ourselves entirely. Ultimately, all human companionship is fragmentary and partial. Human friendship is meant to lead to friendship with God. Human friendship is a valuable and sweet gift and is able to ennoble and elevate the soul, but ultimately, it is a reminder that only God can truly fill the human heart.
Human friendship has limits because of the real greatness of man.
We are too big to be quite comprehended by another. There is always something in us left unexplained and unexplored. Man's limitation is God's occasion.