Marriage is a preview of eternal love. The couple shares in the creative love of God, the Father. For it is true that not only have they been created by Him, they also create with Him in completing and perfecting each other; and of all created love only theirs is generative of a person.
They share in the redemptive love of God, the Son. For it is true that not only have they been redeemed by Him, but they also redeem with Him in every sacrifice of self they make for each other or for their children.
They share in the sanctifying love of God, the Holy Spirit. For it is also true that not only have they been sanctified by Him, but they also sanctify with Him, since every gift of love they make is a "bond of perfection."
The great wonder is, I suppose, that God loves us. The great gratitude is that He does, since as creatures where would we be without His love. An even greater wonder should be that He calls us, as His Image and Likeness, to love as He loves.
Speaking of married love there is not only the wonder, there is also present, as St. Paul says, "a great mystery."
--Msgr. John Knott