Mission of marriage?

"Love is action and not emotion."

Marriage is mission - our purpose is to reflect the relationship between Christ and His bride the church, to be sanctified, growing more into the likeness of Christ, built on the Gospel, proclaiming the Gospel together, perfect, harmonious unity like that of the Trinity, God and His glory at the centre, our love for Him the basis for it all. 

Simply put? It was designed, graciously gifted to us by God, to give us glimpses of His wonderous plan of redemption, reconciliation and restoration, to display the sort of complete and sacrificial love that He has for us shown by Jesus' death on the cross, the process for us for us to be made holy, not necessarily "happy", but to be sanctified, humble, and grow in our dependence on God, who alone can bring true and lasting joy and fulfilment!