One of the greatest things about our long-term romantic relationships is that they can provide comfort and predictability in this wild world we live in.

But let’s face it: Long-term relationships can get a little boring. Within nine to eighteen months, research suggests, 87 percent of couples lose that knee-quaking excitement they felt when they first fell madly in love. It isn’t that these relationships are bad, necessarily; they are just stale. Still edible, but not nearly as delectable as they were fresh out of the oven.

It isn’t just in our romantic relationships: In most aspects of our lives, we get used to the surroundings and circumstances that stay the same; researchers call this “hedonic adaptation.” What was once new and exciting—be it a lover, a new pair of shoes, a new neighborhood, or a new job—nearly always loses its luster over time.

The key word there, though, is nearly: 13 to 20 percent of people in long-term marriages successfully keep the fires of passion alive. (This doesn’t mean that 80 percent of couples are unhappy, it just means that their relationships aren’t particularly sexy or passionate.) And although we adapt to most things in life, we tend not to adapt to circumstances and situations that involve “variable, dynamic, and effortful engagement”—as when we take an engaging hike or class or while we are learning a new sport, according to researcher Ken Sheldon, who studies hedonic adaptation.

All this means that the very predictability that makes our long-term relationships comforting can also make us feel bored and uninterested in our spouses—which, of course, causes disconnection and even conflict. The destructive way to deal with relationship boredom is to seek excitement and novelty outside of the relationship—we all know people who’ve done that. Fortunately, there are better solutions to this common problem.

The antidote: Shake things up. Maybe a lot.

The good news is that its fun to stoke the fires of your relationship. The bad news is that you’ll have to give up some of the comfort (or if not that, the complacency) that has settled into your relationship. Here’s how:

• Make yourself vulnerable (just like you probably were on that first date!). Vulnerability can be uncomfortable because it involves, by definition, emotional exposure, uncertainty, and risk. (Remember: Vulnerability is not weakness!) Vulnerability allows trust and intimacy to develop and deepen.

A simple (if not always easy) way to make ourselves vulnerable in our relationships is to bare ourselves emotionally. What can you reveal to your long-term love that he or she doesn’t already know about you? Ask your beloved intimate questions to which you aren’t sure you know the answer (I carry a little rubber-banded pile of Table Topics for Couples in my purse for just this purpose).

Or do something mildly risky. Go on an adventure for your next vacation, to an unknown place that feels a little daunting. Visit a karaoke bar for your next date night, and actually sing. Try a new sport (where you risk feeling silly or uncoordinated). Do something thrilling, like zip-lining or bungee-jumping.

Vulnerability works in part because it creates a similar biochemistry and physiology as when you and your beloved were first falling in love. Researchers think it is likely that we tend to conflate the high-arousal induced by doing something risky with the high-arousal of intense attraction—the two states feel similar. Either way, an adrenaline rush is good for a relationship that is losing its luster.

• Upgrade your routines. If you’ve been reading this blog for long, you know that I’m a HUGE fan of productive routines and positive habits, and I advocate them in relationships as well, with one caveat: Your relationship habits routinely need to introduce variety, or you’ll start feeling entitled and bored. Making variety a habit—think that’s an oxymoron?

It isn’t. You may have a gratitude ritual at bedtime, where you tell your love something you appreciate about them before sleep; challenge yourself to come up with something new every day. Or perhaps you have a weekly date night—it might be cozy and comfortable to always go to the same Italian restaurant on the corner, but you’re gonna need to shake it up a little bit. Keep the date night, but always do something different. Vary the restaurant, vary the activity. Pretend you are trying to impress a new date.

Even if you aren’t up for the risk of an adventure or the intensity of emotional exposure, make sure there is a little excitement in your relationship routines. When researchers have couples create lists of things that they find exciting to do (maybe skiing, or trying a new restaurant, or going to a part of the city they rarely visit) couples who did something exciting together were more likely to agree with statements like “I feel happy when I am doing something to make my partner happy” and “I feel ‘tingling’ and ‘an increased heartbeat’ when I think of my partner.”

• Surprise your significant other (and maybe yourself at the same time). This is no more complicated than making an effort not to be so predictable. Throw them off their game a bit by blindfolding them on the way to your date-night. Similarly, a good friend and her husband trade off date-night planning, and don’t tell the other anything about the date. They might not end up doing anything outlandish, but the element of surprise makes the situation novel and exciting. Research shows that when ambiguity is introduced into something positive, the uncertainty in and of itself tends to increase our pleasure.

While you’re at it, look for unintended surprises in your significant other. You might be doing something you’ve done with her 1,001 times, but challenge yourself to find something new about the way that she is doing it. Our brains are pattern-finders, and they often see only what they expect to see. We find new people and situations more interesting and exciting because we don’t know yet what patterns we’ll find in their behavior (researchers call this the “lure of ambiguity”). When we find something new about a familiar person, we’ll tend to find him or her more interesting.

In romantic relationships, all of these strategies can (and should) be tried in the bedroom, of course. Lovemaking is one of the most significant ways most couples stay connected, but like the relationship itself, it can get stale over time. Shake things up in your sex life by making yourself vulnerable, taking risks, changing up your routines, and adding elements of surprise.

Finally, do these things as a way to deepen your connection and closeness in your relationship rather than to avoid conflict or rejection. When our relationship goals are positive (e.g., we want to have fun) rather than negative (e.g., we’re trying to avoid a fight), we tend to be much more satisfied with our relationships and to feel less lonely and insecure. And there’s nothing boring about that.

What do you do to add spark back into your relationship?

Interested in learning more about the science behind hedonic adaptation in relationships? I highly recommend Sonja Lubermirsky’s book The Myths of Happiness. There’s a whole chapter on taking your relationship from so-so to exciting!