When what we called the Marital Sabbatical was over and done with and I hit the couch with an aching heart, my therapist asked me to describe my marriage. On paper, and to all outward appearances, we made a great couple. Late thirties, well-educated, healthy and attractive, good jobs. Jim as a handsomely paid associate in a top law firm, me as a conservationist at a top art museum. (“We’re the tops,” I once sang to Jim, a little drunk on both Cole Porter and Veuve Clicquot.) Brownstone duplex...