Marriage as a Path to Holiness - David & Mary Ford
This is an essay included with David & Mary Ford's collection of the lives of married saints. It is the best description of this topic I've ever read. Add to this C.S. Lewis central point about the way we ought to treat one another in general as husbands and wives, not with a lack of respect no stranger would put up with, but with the respect due a Queen by her King, and a King by his Queen - as royalty who have brought their love into God's own Kingdom - with a mutual deference appropriate in the Court of Heaven, and you've pretty much got the whole picture of Christian marriage as we understand it.