My own approach is to think of the Coase theorem. Assume that you can’t redistribute happiness or wealth within the marriage. If your spouse is unhappy you will be unhappy and if your spouse is happy you are likely to be happy; happy wife, happy life. If you can’t redistribute happiness the play to make is to maximize total happiness. Maximizing total happiness means accepting apparent reductions in happiness when those result in even larger increases in happiness for your spouse. If you maximize the total, however, there will be more to go around and the reductions will usually be temporary.

That's Alex Tabarrok on the forgiveness versus tit-for-tat as a strategy for dealing with transgressions in a marriage. Only at Marginal Revolution will you hear the Coase theorem invoked in a discussion about marriage. If I were officiating another wedding I wonder if I could get away with dropping that in my marital advice.

I liked this:

...you really shouldn’t model a marriage as a prisoner’s dilemma.