1 Corinthians 7:4. "For the wife does not rule over her own body, but the husband does; likewise the husband does not rule over his own body, but the wife does."

This sounds like a record scratching to our modern ears, but St. Paul is right. When we marry, we give ourselves to one another fully. We are to hold nothing back, not even our own bodies. This is why contraception is wrong - we are holding something back; this is why withholding conjugal rights is wrong - we are holding something back.

Marriage is a sacramental covenant that is a sign of God's covenant with His Church. God holds nothing back from His bride, and the Church holds nothing back from God. Individually, also, we are to give our whole will over to God, holding nothing back. If we trust God to want only what is good for us, why would we? And if we enter into marriage in the correct state, we should trust our spouses in the same way. Even though our spouses, and we, are fallible, and will let us down sometimes, if we love them unconditionally, the way God loves us, and hold nothing back from them, we are showing God's love to them and the world, the very love that continues to love us even when we fall.