If the purpose of all the Sacraments are to remind and point our lives towards the Glory of God, then it is fair to say that even marriage is to be an act of evangelism. A Christian marriage is one lived in such a way as to exalt Christ, and to proclaim Him. It is not about my personal happiness or fulfillment (Though that is the bi-product of living a life for Christ's Glory). It is about exalting Christ in all things. To do this we must be willing to die to ourselves, and both husband and wife need to be committed to this dying to the self. I think that is why St. Paul said that it was not good for a Christian to be yoked to a non-christian in marriage.
"...some of us are married and some of us are not. Some of us are called to be priests and ministers and some are not. But the sacraments of matrimony and priesthood concern all of us, because they concern our life as vocation. The meaning, the essence and end of all vocation is the mystery of Christ and the Church. It is through the Church that each one of us finds that the vocation of all vocations is to follow Christ in the fullness of His priesthood: in His love for man and the world, His love for their ultimate fulfillment in the abundant life of the Kingdom." Alexander Schmemann in For the Life of the World.