My friend David recently attempted to describe for me the state of his marriage. He explained that he felt like it wasn’t alive but it wasn’t dead. It just sort of kept moving forward, and whenever he thought he might escape it, there it was, lumbering after him. “No matter how fast I run, no matter where I hide, there it is, coming at me like a zombie,” David said. He was joking, of course. But the more I thought about it, the more I realized how much truth there was in the analogy. No matter how strong a union is when it’s forged, inevitably, after the thrilling bloom of the early years, it begins to take on an almost undead quality. It becomes a Zombie Marriage.

“What happens in a marriage is that as it settles,” says Carl Pickhardt, a psychologist in Austin, Texas, “people just get in a routine with each other. They go on automatic.”

The mistake some couples make is diagnosing that comatose phase—when they’re too wrapped up in their careers, kids, and aging parents to engage with each other—as terminal. That’s when they start obsessing over pulling the plug.

“Too many people take that zombie zone as a sign that they need a divorce,” says Susan Heitler, a Denver psychologist and the author of The Power of Two: Secrets to a Strong & Loving Marriage. “The bulk of my practice is referred to me by lawyers, and I’d say 80 percent of those who’d gone in to get a divorce turned out to have great marriages.”

Still, taking the opposite tack—exhaustively trying to jump-start a marriage with therapy, self-help books, and couples’ time that’s enforced as strictly as homework hour—can be equally toxic.

“If I thought I had to work on my marriage all the time,” says one friend who tied the knot 12 years ago, “like constantly take its pulse and make sure everything was okay, I would have given up a long time ago.”

Another friend of mine, whom I’ll call Jeff, says that only when he stopped thinking about his marriage altogether, stopped attempting to prop it up with counseling and “date nights,” and accepted that it was in its zombie phase, did he and his wife settle into a less anxious, more peaceful coexistence. “I’m not fighting it,” Jeff says. “I’m not pretending it’s better than it is.”

These men have realized what a lot of couples who are still together in their fifties already know: In most cases, the Zombie Marriage is just a phase—and quite possibly a crucial one. For a lifelong relationship to survive its most challenging period, it must enter an unconscious, protective state, so that no matter how many stakes are driven through its heart it will continue to stumble forward.

Accepting that isn’t a license to stop caring. It doesn’t mean you can start avoiding home and ignoring your wife when she has something to say. Nor can you get away with using a marital coma as an excuse to cheat.