A good priest's job is to lay out for the couple a theological/mystical basis for their union so that each spouse intellectually, spiritually enters into the union with a firm understanding of the notions and implications of "sacrament" and of a "covenant" sealed and made before God.
Marriage as a sacrament is designed to prepare each spouse for eternity, to bear witness the love of Christ to each other, and to procreate. THat's how the unmarried men Jesus and Saint Paul described it in the New Testament.
Not saying there isn't room for secular therapy, but that the sacramental/mystical basis is so often set aside. And people's understanding of the spiritual magnitude of the union is diminished from the get-go. Marriage is NOT "eternal" (only Mormons believe that) -- but it's supposed to serve as an earthly testimony of Christ's eternal union with his people, the church.
“For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh.” This is a profound mystery—but I am talking about Christ and the church. However, each one of you also must love his wife as he loves himself, and the wife must respect her husband. ~ Ephesians 5:31-33
Remember Christ is married. His bride is the Church.