Human beings are social creatures. We suffer if we feel lonely and thrive most in the company of those who love and accept us. Our first experience of this love is within our family. The family is where we first encounter the love of other human beings. God love us, but His love is often most clearly shown to us through the love of other people. The love which we have for each other is part of the love of God. All love comes from God, and all love reflects that love that God has for all of His creation. We call God "Father," but we only understand what this means because we have an idea of what a human father ought to be like: loving, patient, and generous.
Human beings are sexual creatures, and for most people sexual love is the closest form of union they will ever know. The love which a couple have for each other mirrors the love that God has for men and women. The sacrament of marriage is, first and foremost, a sacrament of this love. The couple echo the words of Christ which are spoken in the Mass: "This is my body, which is given up for you." The sacrament of marriage becomes the sacrament of Christ's love for the whole world. The self-gift of the Eucharist is made truly visible in the love between the married couple.