God's plan for the marriage covenant involves the following of some vital principles:
The permanence of marriage: Marriage is intended to be permanent, since it was established by God (Matthew 19:6; Mark 10:9). Marriage represents a serious commitment that should not be entered into lightly or unadvisedly. It involves a solemn promise or pledge, not merely to one's marriage partner, but before God.
The sacredness of marriage: Marriage is not merely a human agreement between two consenting individuals (a "civil union"); it is a relationship before and under God (Genesis 2:22)
The intimacy of marriage: Marriage is the most intimate of all human relationships, uniting a man and a woman in a "one-flesh" union (Genesis 2:23 -25). Marriage involves "leaving" one's family of origin and "being united" to one's spouse, which signifies the establishment of a new family unit distinct from the two originating families. At its very heart the concept entails the establishment of a new kinship relationship between two previously unrelated individuals (and families) by the most intimate of human bonds.
The mutuality of marriage: Marriage is a relationship of free self-giving of one human being to another (Ephesians 5:25-30). The marriage partners are to be first and foremost concerned about the wellbeing of the other person and to be committed to each other in steadfast love and devotion. This involves the need for forgiveness.
The exclusiveness of marriage: Marriage is not only permanent, sacred, intimate, and mutual; it is also exclusive (Genesis 2:22-25; 1 Corinthians 7:2-5). This means that no other human relationship must interfere with the marriage commitment between husband and wife.
The married couple themselves administer the sacrament of matrimony to one another. Sacrament is understood as "a visible sign of an inward grace." Married life is sacramental because the love of God is revealed through the married couple's love for one another. Whether we look at the marriage ceremony or the life that unfolds from it, the man and woman's gift of each to the other is the sacrament. It is the place where God appears.
What is Christian Marriage?
Marriage is a covenant, a sacred bond between a man and a woman instituted by and publicly entered into before God and normally consummated by sexual intercourse.
"The eucharist is the very source of Christian marriage. The Eucharistic sacrifice represents Christ’s covenant of love with the Church, sealed with his blood on the cross. In this sacrifice of the new and eternal covenant, Christian spouses encounter the source from which their own marriage covenant flows, is interiorly structured and continuously renewed."
Pope St.John Paul II
When a man and a woman marry in the Catholic Church they promise to give themselves freely, fully, faithfully to each other until death and they agree to accept children willing from God and to bring them up in the faith. In giving themselves freely a person is saying "it is my choice to spend the rest of my life with you. No one and no situation is coercing me to do it."
In giving themselves fully to each other, husband and wife are not just offering "to meet you half way". It is not a 50/50 relationship. They are saying I want to live my life for you and for your salvation. It is a 100/100 relationship which finds its ultimate expression in the physical self-giving of their love that holds nothing back.
Sacrament of Marriage