(CNN) — Remember the last time you fell in love? If you are like many people, you probably found yourself craving the moments with that person — just sitting side by side, sharing laughs over a meal or slipping sex into otherwise busy schedules.

We enjoy the company of the person we love. This preference for time spent with someone we love is not limited to humans — it also shows up in prairie voles and primates. And research shows spending time with a loved partner seems to be good for us.

Years into a relationship, however, many of us feel stable with our partner, and other priorities can compete for our time. We might go back to working late; perhaps kids come into our lives, or we stay up late to finish a favorite TV show rather than going to bed with our partner. But what if we could reignite a motive to draw us closer to our partners, reclaiming those enjoyable stolen minutes?

Decades of research on human behavior suggests it is harder than it sounds. People get into habits, and, despite our best intentions, those habits are hard to change.

Recently, my research collaborators and I tried an approach to helping people get more moments with the person they love by working with human nature rather than trying to fight it.

Here’s how.

We thought we could help people express gratitude to their partner when they felt it, and these expressions of gratitude would draw the couples closer by spending more time together. Why gratitude? It’s an emotion that reminds us of what we like about our partners in the first place.

To get there, we developed a brief technique to help people show it. Participants in the study made a plan to express gratitude to their partner when they felt it. (Research in other areas, such as exercise and recycling goals, shows developing a plan helps sidestep willpower, making it more likely we’ll do what we are already motivated to do.)

Critically, this was not a time-intensive session. It was a self-guided exercise that took less than five minutes, one time, for just one member of the couple.

Just making the plan had a positive impact — people in our study realized there were lots of things their partner did for which they felt grateful. They said they were grateful to their partner for things such as rubbing their back, making them laugh, giving them a compliment, listening when something was bothering them, helping when they were sick, spending time with their family, making them a meal and even watching sports together.

In our five-week experiment, we found that this technique worked. The participating couples increased time with their beloved by an estimated 68 minutes per day, on average, compared with those in the control group (who were not encouraged to do anything differently during the five weeks). Expressing gratitude physically drew partners closer together.

We know what they were doing in those minutes over 35 nights because they told us. Couples reported spending significantly more time hanging out together, sleeping in the same bed or simply being in the same room together but doing their own thing, compared with couples in the control group.

Some days it was much more than an hour, and some days much less. I suspect they slipped in the time when they could, eating breakfast together one day, coming home on time rather than working late at the office and sometimes spending an entire day together.

Gratitude for the things they appreciated about their partner drew them together. And it didn’t take hours and weeks of training or learning an entire suite of new skills. It’s simply the upward spiral that gratitude set in motion.

What do I mean by upward spiral? Well, the mere fact that my partner does something to benefit me does not necessarily trigger my gratitude. (Sorry, honey!) Research shows that emotional response is reserved for times when I perceive that he’s gone above and beyond.

But when we do feel gratitude, that little burst of emotion draws our attention to what we love about our partner and motivates us to show them that we care, too, often through an expression of gratitude. In turn, hearing an expression of gratitude makes the listener feel good about themselves and the relationship. In one study of romantic couples, those good feelings forecast the likelihood of spontaneously kissing their grateful partner later in my lab!

To set this in motion naturally, we needed people to notice when they felt grateful to their partner in everyday life and then to express their (real) gratitude. So, we turned to “if-then” planning. This is a technique that gets people to identify opportunities to do something they already know how to do — such as express gratitude — and make a brief plan to do it when they have the chance. The exercise works toward an easy-to-remember plan: “If my partner does something I appreciate, then I will express my gratitude.”

In everyday life, romantic couples are constantly doing things for one another that might be appreciated — there are lots of opportunities.

To be sure, we are still tinkering with how to make this work for everyone. In this study, it worked best for the two-thirds of people who were naturally more inclined to express gratitude in their everyday lives before making the plan. For the other one-third, we need to keep working. (There was no downside, but we have no evidence this brief task was effective for them.)

We are also capitalizing on authenticity. In my team’s first attempt to change relationship outcomes through gratitude expressions, it was much more involved for the couples: Both people sat down a few times over a month to express gratitude to one another face-to-face. It didn’t work, and I suspect it was because we were forcing what needs to come naturally.

This study is one small step in that project, but as a first of its kind, it holds a lot of promise. The joyful comfort of time with a loved one makes days happier and our lives healthier. It may be impossible to recapture the giddy joy of falling in love, but it doesn’t take much to rediscover the things we love about our partner and strengthen our relationship in the process.

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