A therapist explains why one of the most traditional beliefs about marriage is also the most damaging

Imagine accepting a job you had to stay in forever. Even if the pay stagnated, or there turned out to be no room for advancement, or your coworkers consistently brought in smelly lunches, you'd be legally obligated to stick it out.

The thing about marriage is that you're essentially taking the same leap of faith.

Sure, marriage is different — it's about love and passion and trust in much greater quantities than are present in the workplace.

But still, you're projecting yourself 20, 40, maybe even 60 years down the line and imagining that you and your partner will stay in just the same position as you are right now.

It's something Susan Pease Gadoua has thought a lot about. Pease Gadoua is a therapist and the founder of the Changing Marriage Institute; in 2014, she and Vicki Larson published a book titled "The New I Do," in which they argue against the one-size-fits-all marriage.

When I spoke with Pease Gadoua in June, I asked her if it was useful to keep the possibility of divorce in the back of your mind.

She told me: "When people see divorce as never an option, it can create some unhealthy dynamics."

Of course, the alternative — acknowledging that one day you might not want to be with your partner anymore — sounds terribly unromantic, not to mention impractical. Who wants to marry someone who thinks they might wake up one day and want out?

Pease Gadoua explained it in general terms. "Someone who has to stay in anything — be it a job or a marriage — that doesn't usually bring out the best in us," she said. "We tend to do best as people when we feel like we have a choice."

In other words: simply knowing that you have an "out," as Pease Gadoua called it, is freeing, even if you never use it.

The existing concept of marriage, she said, is really a "shame-based model." There's this idea that "you made your bed; you have to lie in it." In other words, you married this person thinking you could be with them forever, and now you have to live up to that expectation.

But Pease Gadoua mentioned research by Harvard psychologist Daniel Gilbert, which found that most people have no idea how much they'll change, and what they'll want out of life, a decade from now.

The implication for marriage is, if you accept that you might grow out of your relationship — or your partner might — you're freeing yourself to be in the marriage because you want to, and not because you have to.

That said, no one's arguing that if you feel a blip of boredom or frustration with your relationship, you should bolt. In the book, the authors propose the idea of a "relationship contract" that you and your partner regularly review and decide whether to renew.

It's a way of making sure that the relationship is evolving to meet both partner's needs and wants. (Still, as my colleague Erin Brodwin reported, the contract is a somewhat controversial idea among relationship experts.)

The main takeaway here is about being realistic. Love is a commitment — passion may fade, and there may be days when you want to strangle your partner, and still you stay. That's love.

But knowing that you can leave if you're truly dissatisfied with the marriage, or if you realize that your partner's notion of marriage doesn't jibe with yours, is somewhat reassuring.