Rumi, the 13th-century Sufi poet, famously compared emotions—“a joy, a depression, a meanness”—to “unexpected visitors.” His advice was to let them in laughing, but that’s not what we do. Instead, we pretend not to notice, or even hide. We want to bury resentment and anger, or trade loneliness in for the more fashionable gratitude.

In a cultural age that’s decidedly pro-positivity, the pressure to suppress or camouflage negative feelings is real.

However, psychological studies have shown that acceptance of those negative emotions is the more reliable route to regaining and maintaining peace of mind. Whether practiced through the lens of ancient Eastern philosophies, or in increasingly popular forms of treatment like Acceptance and Commitment Therapy and Mindfulness-based Cognitive Therapy, acceptance of one’s dark emotions is now backed by a body of evidence connecting the habit to better emotional resilience, and fewer symptoms of depression and anxiety.

Acceptance, therefore, is having a moment—at least among academics. But how and why it works has been little studied, says Brett Ford, a psychology professor at the University of Toronto. Not quite a strategy, she tells Quartz, “acceptance involves not trying to change how we are feeling, but staying in touch with your feelings and taking them for what they are.” So, she asks, how can it be that accepting negative emotions is paradoxically linked to long-term psychological thriving?

A few years ago, when Ford was a doctoral student at University of California, Berkeley, she and three fellow Berkeley researchers devised a three-part study to try and find out. Their findings were just published in the Journal of Personality and Social Psychology.

According to their analyses, the magic of acceptance is in its blunting effect on emotional reactions to stressful events. It’s that mechanism that can, over time, lead to positive psychological health, including higher levels of life satisfaction. In other words, accepting dark emotions like anxiety or rage, won’t bring you down or amplify the emotional experience. Nor will it make you “happy”—at least not directly.

“You always interpret null effects very cautiously,” Ford says, “but to us, it appears that acceptance uniquely affects negative emotions, and isn’t interfering with positive emotions.”

What’s more, acceptance seems to be linked to better mental health when it’s used in response to negative emotions, not positive ones, she adds, so this is not about living in the world with a “broadly detached attitude.” No need to play it too cool.

Fortunately, acceptance works for a diverse range of people—the researchers found it’s not bound to one socioeconomic or racial group. It also appears to be effective whether people are dealing with feelings related to intense life events or minor inconveniences.

Finally, they assert, acceptance is more connected to better psychological health than other mental modes that fall under the general umbrella of “mindfulness,” such as practicing non-reactivity, for instance, or simply observing. “You need to pay attention to your internal experience,” says Ford, “but acceptance, non-judging acceptance, seems to be the key ingredient to mindfulness.”

Three Tests of Acceptance

Ford’s findings were drawn from at least one and often two parts of the three-part study.

First, researchers analyzed responses from more than 1,000 questionnaires focused on emotional regulation and psychological health sent to undergraduate students at University of California, Berkeley. Habitually accepting negative emotions was found to not only reduce feelings of ill-being (which previous studies had demonstrated), but also was more likely to lead to elevated levels of well-being.

Next, the psychologists recruited 156 people from the San Francisco Bay area for a lab experiment that subjected participants to standardized universal stressor: a public speaking task. “We had people show up and we told them, ‘By the way, you’re going to give a three-minute speech pretending you’re at a job interview and you have to talk about your verbal and written communication skills,’” Ford says. The hypothesis was that those who had been identified as more accepting of their negative mental states would report less severe negative emotions, which was proven to be true. Again, the researchers were building on the work of other psychologists, but, they also tested the robustness of the accepting method by ensuring that at least half of the selected participants had experienced a major negative experience, such as being cheated on or losing their jobs in the months before the study.

In the last study, the researchers asked 222 people of various races and socioeconomic backgrounds, this time recruited from the Denver area, to keep a diary in which they recounted the most stressful event of each day over a two-week period. Their baseline acceptance habits were measured before the diary-writing period, and their general psychological well-being was measured through standardized questionnaires six months later. Habitual acceptors, let’s call them, fared better than their peers, whether the incidents they wrote about were heavy (receiving a phone call from a son in prison, for instance) or relatively mild (minor arguments with a significant other was a common stressor.)

Resist the Urge to Strive for Happiness

Buddhist leaders often underline that “acceptance” doesn’t mean being resigned to a stressful, negative situation, especially when the situation is within your control. Accepting situations is more complex and context-dependent, says Ford. We need to accept a death, but we don’t need to endure unfair treatment from a landlord or employer, for instance, and doing so might lead to worse mental health.

Negative emotions are different, because they’re an unavoidable part of being human. “Life is wonderful from time to time, but it’s also tragic,” as Svend Brinkmann, a psychology professor at Denmark’s Aalborg University, told Quartz’s philosophy reporter Olivia Goldhill. “People die in our lives, we lose them, if we have only been accustomed to being allowed to have positive thoughts, then these realities can strike us even more intensely when they happen—and they will happen.”

The other problem with only allowing ourselves to think positively, and constantly pursuing happiness, is that it puts people in a striving state of mind, says Ford, and that is antithetical to a state of calm contentment.

Ford believes her research could help inform future mental health interventions, which currently rely on some approaches that can fail people. “When something happens and you try to reframe it like, ‘Oh it’s not of such a big deal,’ or ‘I’m going to learn and grow from that that,’ it doesn’t necessarily work,” says Ford. People tend to reject that kind of reframing when their issues are severe, too.

That said, acceptance remains mysterious in some ways. Psychologists don’t know which factors influence some people to habitually accept less-than-rosy emotions, despite cultural pressures to stay positive. It’s also unclear whether acceptance might backfire in some individuals, or if people who usually suppress their darker feelings could seamlessly make the transition without the aid of a therapist or zen teacher.

“My hunch is that it’d be a challenge,” says Ford. In the West, and in the US, especially, she says, happiness and positivity are seen as virtues. “Some companies want their customers and employees to be delighted all the time,” she says. “That’s unreasonable, and when we’re faced with unreasonable expectations, it’s natural for us to start applying judgment to the negative mental experiences that we have.”

Like other cognitive habits, however, acceptance is a skill that can be acquired. (One commonly taught tactic is to think of your emotions as passing clouds, visible but not a part of you.) And according to a study Ford co-authored in 2010, older adults use acceptance more than younger adults. Like wisdom, the trait tracks with age, so most of us will get there eventually.