We, as humans, are given a high honor. We were created with the ability to love and to communicate that love to one another. Marriage is a unique, even divine, expression of that love. The love a husband and wife have for each other serves as a picture of God's love for the world. In that, it is a serious calling, not something to be taken lightly. Not just because one is responsible for the other but because one is responsible for how the world views their relationship with the other. Marriage is serious, holy business because it is meant to reflect God in His most intimate potrayal.
For that matter, the love we have for each other (married or not) is a picture of God's love for the world. God loves the world; that goes without question. The problem is, the world doesn't know that yet. How are they supposed to see that if we aren't showing them?
My little children, let us not love in word, neither in tongue; but in deed and in truth.I John 3:18