What a difference a spectrum can make, though, because those at the other end of the quashing range — the appreciatively resigned — seem to be among the healthiest and happiest of the marrieds.

Not much sexual passion left in the marriage? That’s offset by what’s left. Like Dr. Seuss’s Whos down in Whoville who hold hands and sing after being robbed on Christmas Eve of all their food and possessions, the appreciatively resigned rise each morning not dwelling on their marital shortfalls but counting their mutual blessings, whatever they may be: a shared sense of humor, an exchange of kind gestures, the enthusiastic pursuit of a mutual interest. Somehow they have managed to grow together rather than apart.

THE RESTORER. When a restorer couple’s marriage starts to feel subpar, they sit down and have a sensible discussion about where their marriage is and where they would like it to be. Then they set goals and seek the means to achieve those goals. Typically affluent, educated and highly motivated, restorer couples almost single-handedly support the vast and profitable marriage-improvement industry.

It won’t take long for them to find out that, surprisingly, the most recommended strategy for reigniting passion in marriage — passion that has waned in part because of the deadening weight of its routines — involves loading up the relationship with even more routines: date nights, couples counseling, dance classes, scheduled sex, 10 for 10s (committing to 10 hugs of 10-seconds in duration every single day), fresh flower Fridays (a boon to the local florist, if not your marriage), required kisses upon parting, lunchtime exchanges of erotic texts, and possibly some creative midday play at the local Holiday Inn involving silk scarves and an eye patch.

Such restorative activities fall into two groups: drudgery and spice. The drudgery, like research and couples counseling, is supposed to be hard work, whereas the spice, such as “creative” bedroom play and kisses upon parting, is supposed to be fun. Depending on a couple’s proclivities, however, the drudgery may turn out to be fun (like reading to each other in bed from marriage improvement books) and the attempts at spice may start to feel like work (having to get out of the car and go back inside because you yet again forgot your required parting kiss).

These attempts at relighting the flame may work for some, but for others they seem to be less about feeling sexy or “rediscovering” each other than they are about demonstrating a nose-to-the-grindstone determination to try anything to stay together and remain vital, which can have a bonding appeal of its own.