Grace, by definition, is unearned and undeserved. God has shown us the way by giving us grace, which has worked out rather well for those of us who accept His grace.
How about we look for ways to extend grace to our wives? Not when they are being nice, or things are going well, but when they are being less than nice (maybe even downright ugly) and when things are going less than well (maybe even horrible). Just whip out the grace card, apply, and move on.