What happens to your brain when you are stressed. And how to build mental toughness

When you hear the term mental toughness, what comes to mind? How would you explain it to someone? Poise or staying cool under pressure, confidence, composure, focused: all accurate descriptors I have heard that add up to the ability to handle and mitigate the human fight, flight, or freeze stress response. The problem with these words is that they all describe an end state, but not how to get there. If I ask you to describe physical toughness, you can likely describe the end state (strength, resilience, and so on), as well as the way to get there (rigorous training, exercise, pushing yourself). You know what to do. What about mental toughness? What’s the training and exercise for that? Besides being chased by a bear?

Everyone experiences stress. (Technically what we experience are stressors, which lead to the human stress response. Stressors + human stress response = stress.) Excellence stems from how well you react to it, how you maintain your ability to think clearly, make decisions, and act. This is the foundation of elite performance, but elite performers are not born with this ability. The best athletes, performers,  businesspeople, leaders, and soldiers all start with the same innate stress response we all have, but as they grow they get help and practice in overcoming it. They have the support of parents, coaches, mentors, and fellow performers, and have lots of chances to perform from a young age, learning how to overcome (or buckle under) pressure and get better at handling it. They pick up stress inoculation, mostly unintentionally, through trial and error.

Many of us don’t have the benefit of this tutelage but we can still all learn how to get better at handling the human stress response; we can practice mental toughness. There are several exercises that can help you get better at handling the human stress response, so you can call on mental toughness when stressful scenarios arise. The techniques I describe are designed to help mitigate the real-time effects of human stress response to improve performance.

Go back to prehistoric times and imagine a saber-tooth tiger charging a pair of cavemen. Caveman Fred observes the beast and carefully analyzes his options. Caveman Barney scrams. Fred, a thinker, gets eaten by the beast and becomes the central figure in a Flintstones funeral. Barney, whose thinking takes a backseat to action, survives the attack and gets to pass his genes on to subsequent generations. He has developed what we today call the hypothalamic-pituitary-adrenal (HPA) axis, the fulcrum of the human stress response. While we may be fans of Fred, we are descendants of Barney.

The HPA axis is a body system that spots incoming danger and releases hormones to prime our response. When the human body experiences stress, like a charging bear or tough interview question, the hypothalamus gets to work and the sympathetic nervous system is now on full alert. This all happens quickly, faster than the brain is able to process what it is seeing and hearing. The body acts without thinking.

That’s the physiology of the stress response. The reality is a bunch of physical and cognitive changes. Heart rate increases to improve delivery of oxygen to muscles and organs. Vessels constrict, so that blood stays with vital organs (caveman Fred can lose an arm to the saber-tooth tiger and not bleed out as fast). Blood pressure goes up. Pupils dilate to let in more light and improve vision. Small airways (bronchioles) in the lungs open up, bringing in more oxygen. Senses become sharper, and additional sugar and fats are released into the bloodstream, boosting energy. Muscles get tense, breathing gets rapid and shallow, and sweat and tears start flowing. Digestion slows down; why worry about it when you’re faced with grave danger?

Most critically, executive functions in the brain’s frontal lobe diminish. Advanced problem solving, judgment, and decision making become impaired. It’s harder to concentrate and remember things, thoughts race, and things get more confusing. Thinking takes time, a precious commodity when faced with imminent demise. Your body’s HPA wants you to act, not think.

This was all an immense help back when fighting, fleeing, or freezing were the only options our ancestors had when facing danger and a second’s hesitation could be the difference between life and death. Today, though, it’s usually a hindrance. In today’s stressful situations, we need to think and analyze on the fly, which is hard to do without a frontal lobe. We might need fine motor skills in our extremities, which is more challenging to come by with less blood flow. For example, the core competencies of Navy SEALs are their ability to shoot, move, and communicate. All of these are compromised by the human stress response.

Furthermore, there are a lot more stressors than there used to be. Our ancestors’ lives were dull compared to what we experience today. Sure, maybe there was that occasional saber-tooth tiger skulking about, but there was no traffic on the commute from the cave to the hunting and gathering grounds and no bosses asking for a 360-degree review on how you threw the spear or created fire. Mastering the response isn’t just important for performance; it can also be vital for health.

I think of the stress response like a series of dominos set up in a row. When a stressful situation triggers the hypothalamus into action, that’s like tipping the first domino. All of the other dominos, from the release of cortisol and adrenaline and the accompanying physical and cognitive effects, are sure to fall shortly after the first one does, unless the chain reaction is somehow stopped. This is what stress inoculation does.

Excerpted with permission from Learned Excellence: Mental Disciplines for Leading and Winning from the World’s Top Performers (Harper Business) by Eric Potterat and Alan Eagle. Published on February 6, 2024 by Harper Business, an imprint of HarperCollins Publishers.