There's one thing that keeps a marriage happy and healthy, and it's surprisingly simple.

We all dream of happily ever after, right? The kind of love that stands the test of time. For better or worse. In sickness and in health.

But here's the thing — relationships are hard work. And marriage? Even harder.

You know those little niggling feelings you get sometimes? The ones you brush off or tell yourself you're overthinking?

Well, they might actually be your gut trying to tell you something important about where your relationship is headed.

A 2023 interview with Harvard social science professor Arthur Brooks has been doing the rounds lately, and for good reason. After studying love for more than 25 years, Brooks identified the one thing that keeps couples together — and the key signs you could be heading for divorce.

According to Brooks, one of the greatest predictors of divorce is when you experience loneliness while living together.

Ever felt isolated while with your person? Yeah, this one hits close to home for many of us.

Watch: What really happens to couples after kids? Post continues below.

Brooks points to empty nest syndrome as a perfect example. He says it's often not the fact that the house is suddenly child-free that parents struggle with.

"It's the fact that there only was one other bird, and they don't really like that bird very much," he said.

But here's the uncomfortable truth; once kids grow up and leave home, you're suddenly confronted with a stark reality — the only thing you had in common was your children.

"That one point of commonality disappears, and you're sitting across the table blinking at each other during dinner not talking because you literally don't have anything to talk about," Brooks said. "That's metastatically awful for a relationship."

So, how do we avoid this relationship death trap?

"It's critically important that couples have something in common besides their kids," Brooks said.

Sounds simple enough, right? And honestly, it can be anything; practising religion together, sharing hobbies, reading similar books or just discussing the big, meaningful stuff in life.

Brooks' "gold standard"? When your children actually witness you having deep, meaningful conversations with your partner. It shows them (and you) that there's a rich intellectual or spiritual connection that goes way beyond just being co-parents.

"It's got to be something that's bigger than changing a diaper because you know that that's not going to be something you have in common forever and you're going to be lonely inside your relationship," he said.

The real secret to lasting love.

So what's the antidote to relationship loneliness? According to Brooks, it's surprisingly simple.

The thing that keeps a marriage going strong is this: be genuine friends with your partner.

Brooks calls it companionate love: "a partnership with somebody who will be the last person on whom you lay your eyes as you take your dying breath."

And here's something that might actually reassure you: while passion naturally ebbs and flows (and that's completely normal), this deeper friendship endures.

In fact, Brooks says those passionate highs and lows are "completely okay," "healthy, normal, and actually advisable" for long-term sustainability.

"You must be close friends, ideally best friends, with your spouse," Brooks said.

"Til death to us part… that has to be the juice of the relationship, or the love that actually makes true happiness. And love truly is the great secret of happiness, that's the one Saving Grace."

And isn't that what we're all really after?

Feature image: Titova Ilona/Canva.

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