Pharisees seemed to trap Jesus by asking him about the legal grounds of divorce. Jesus refused to reply yes or no. Instead he pointed him back to genesis, where God states his original intention for Humanity. Only by discovering that plan, can we fully understand questions about sex and marriage. Hardness of the heart and family breakdowns are no longer inevitable consequences of sin. There is a new phase enabling us to experience what God intended.
We all absorb certain attitudes about the body from the world around us. Our own culture's tendency is to idolize, and at the same time demean the body. For example, any advertisement not based on exploiting the body for its sex appeal is likely to be based on indulging the body, wether it's through food, hormone treatments, or thrilling experiences.
God calls us to be in communion with one another, and treat others the way we want to be treated, and as His children, we must live with one another. Like the Trinity, marriage is a communion of love between people. This love is witnessed through the family that is called to live in loving harmony with one another.