In this same way, husbands ought to love their wives as their own bodies. He who loves his wife loves himself.This is how it was from the beginning. Jesus tells us that a man is to leave his father and mother and cleave to his wife, and "they will become one flesh." (Read Mark 10:1-12)
Why is marriage a holy and sacred thing?
Marriage is a holy and sacred thing because God said it was a holy and sacred thing. He "invented" marriage for more than just procreation. Procreation can happen outside of marriage, if no one has told you yet... Marriage is more than that. It is a picture, and I will say it every time that I write on this topic. God hates divorce (Malachi 2:16) for all of these same reasons.
In this verse, the emphasis is put onto the man, the husband. He is commanded to love his wife, "in the same way" as this love that Jesus has had for His church. It is a tall order, but we do it to fulfill our vows to Christ.