What scares you? Terrorism? Climate change? Snakes? Germs?

Whether it makes you buy a handgun or hand sanitizer, an electric car or an electric fence, fear drives much of human behavior. And it’s not just fear of physical harm that makes us want to hide under the covers. The twin fears of intimacy and rejection, for example, shape many of our social interactions.

Scientists say fear and its companion — the fight, flight or freeze response — can save us when faced with imminent physical harm.

This served us well when we were cave dwellers, under constant threat from marauding wild animals or invading warrior tribes. But it can often get in our way in modern life.

“Change has occurred so rapidly for our species that now we are equipped with brains that are super sensitive to threat but also super capable of planning, thinking, forecasting and looking ahead,” said Ahmad Hariri, a professor of psychology and neuroscience at Duke University. “So we essentially drive ourselves nuts worrying about things because we have too much time and don’t have many real threats on our survival, so fear gets expressed in these really strange, maladaptive ways.”

Dr. Hariri studies the amygdala, an almond-shaped structure that has been called the seat of fear (there’s one in each hemisphere of the brain). But it’s really the seat of anticipation. The amygdala primes you to react — your pulse quickens, your muscles tense and your pupils dilate — even before other parts of your brain can figure out if you need to be scared or not. We are particularly sensitive to anything new, other people’s fearful facial expressions, or anything that resembles something that harmed us in the past.

It’s why you jump when you sense rustling in the bushes before realizing it’s just your neighbor’s cat. That reflex can save your life in certain circumstances such as leaping out of the way of an oncoming car. Trouble starts when you can’t tamp down your amygdala’s response, which makes you obsess and perhaps do counterproductive things when faced with concerning but not life-threatening events like the Equifax hack or a vulnerable social situation like asking someone out on a date.

Consciously activating the more measured, analytical part of your brain is the key to controlling runaway fear and anxiety.

But it’s not so easy in an era when social media and cable news make us aware of every actual or potential disaster occurring anywhere in the world (and in a repeating loop). It’s even more difficult if you have lots of stress or instability at home or work.

To your primitive mind, it’s as if there are lions and tigers lurking around every corner.

The result is often a juiced-up amygdala more apt to flip you into fight, flight or freeze mode in response to even the slightest concern, and keep you there, rather than return you to a state of calm in the absence of clear and present danger.

Remaining in this state of wary hypervigilance can contribute to issues like social anxiety, hypochondria, post-traumatic stress disorder, insomnia and all manner of phobias. It also plays a role in racial and religious intolerance because fearful people are more inclined to cling to the familiar and denigrate the unfamiliar. According to the National Institute of Mental Health, roughly 18 percent of the United States population is afflicted with persistent, outsized fear responses to seemingly ordinary stimuli.

Arresting an overactive amygdala requires first realizing and then admitting you’re feeling uneasy and scared.

“Our culture valorizes strength and power and showing fear is considered weakness,” said Leon Hoffman, co-director of the Pacella Research Center at the New York Psychoanalytic Society & Institute in Manhattan. “But you are actually stronger if you can acknowledge fear.”

That’s how it was for Sean Tucker, a pilot who for 40 years has performed heart-stopping aerobatic stunts at air shows despite an almost paralyzing fear of crashing.

“I never told anyone how scared I was when I started flying,” Mr. Tucker said. “But what I learned was that fear turns into a self-fulfilling prophecy and if you have the courage to admit it, you’ll be able to focus and prepare and rise above it.”

If you can sense and appreciate your fear — be it of flying, illness or social rejection — as merely your amygdala’s request for more information rather than a signal of impending doom, then you are on your way to calming down and engaging more conscious, logic-dominated parts of your brain. At that point, you can assess the rationality of your fear and take steps to deal with it.

“The more you try to suppress fear, either by ignoring it or doing something else to displace it, the more you will actually experience it,” said Kristy Dalrymple, a clinical assistant professor of psychiatry and human behavior at Alpert Medical School of Brown University.

Dr. Dalrymple is a proponent of acceptance and commitment therapy for managing fear, which has recently been gaining clinical validation. It encourages people not only to accept that they are feeling fearful and examine the causes but also to think about their values and how committing to overcoming their fears would be consistent with who they want to be. The approach forces higher-order thinking, which theoretically disables or diminishes the amygdala response.

The classical pianist Emanuel Ax, whose career demands that he perform in front of thousands of people, has long struggled with stage fright. He didn’t go to a psychotherapist, but it seems that the strategies of acceptance and commitment are how he manages his fear.

“I’m still scared, but I’ve learned to accept that I’m going to be nervous,” Mr. Ax said. “Aside from being what I love to do, playing the piano is my employment and gives people pleasure. I wouldn’t be doing my job if I gave in.”

Psychologists and neuroscientists are also finding that the amygdala is less apt to freak out if you are reminded that you are loved or could be loved. For example, seeing images of people with frightened expressions is usually a huge trigger for the amygdala, but that response is greatly diminished when subjects are first shown pictures of people being cared for or hugged.

Just as fear can be contagious, so can courage, caring and calm.