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How the Brain Works (and Why Change Is So Hard)

Why is change so exhausting? How the brain works, explained through System 1 and System 2, the amygdala and the prefrontal cortex.

You are not your mind. You're watching the output of a system that's running. And that changes the whole point of view.

What Happens in the Brain

The human brain, with its roughly 86 billion neurons organized into complex networks, is the system from which everything we call “mind” emerges: thoughts, decisions, interpretations. But in many ways its functioning is still prehistoric: it tends to favor, when it can, the solutions that require less energy and less processing time, not necessarily the ones most useful for our wellbeing.

Left untrained, the mental processes behind our decisions tend to follow this same energy-saving logic. At the behavioral level, it does this through habits and routines, resisting sudden changes even when they're useful or necessary. This is why changing behavior is so exhausting. At the decision-making level, it looks for quick, cheap solutions, relying on heuristics and cognitive biases: mental shortcuts that let you reach quick conclusions, at the cost of lower accuracy.

Eighty-six billion neurons, and most of that work goes toward not wasting energy rather than toward finding the single best choice. Worth remembering every time you expect fully rational choices from your own brain.

Why it matters

Understanding this underlying mechanism matters because it explains, without moral judgment, why change is so often exhausting, and why the mind, when it thinks it's reasoning clearly, is often just following shortcuts that expose it to cognitive traps, hasty judgments and poor choices. This isn't a personal flaw, but the way the brain has learned to function over hundreds of thousands of years of evolution oriented toward survival, not wellbeing.

How System 1 and System 2 Work

The brain uses two major decision-making systems. System 1 makes fast decisions, uses little energy, and doesn't trigger deep reasoning. System 2 makes elaborate, reflective, deliberate decisions, weighing the available options: it uses far more energy, and the brain doesn't like that, even though it can be trained through the right strategies and routines. The brain always favors System 1, because it better serves its primary goal of saving energy, regardless of the quality of the decisions made. Every time System 2 gets tired, decision-making gets rerouted to System 1: hence the importance of breaks and pauses during work that demands maximum attention.

The brain is, in a sense, wired to keep answering two questions: is this a threat? Is this an opportunity? The amygdala is one of the structures involved in the immediate emotional response to external events. The prefrontal cortex, involved in more deliberate and reflective processes, offers the possibility of consciously choosing how to respond to those events, giving them the most useful meaning. Neither works alone, though: emotional responses involve networks distributed across the whole brain, not a single dedicated area.

What we call emotion is, in this framework, a physiological process: chemistry, breathing, posture, the speed of thought and the quality of attention all shift. The brain can be compared to a bartender mixing different cocktails: adrenaline and cortisol when alertness is needed, serotonin, endorphins and oxytocin when pleasure, bonding or recovery is needed. Repeating a state several times doesn't make it character: it simply makes it easier to reproduce. This is one of the foundations of experiential learning: what you train becomes more quickly accessible.

Common mistakes

A common mistake is considering your own decisions always rational and deliberate, without recognizing how often they actually come from System 1, especially when tired or stressed. A second mistake is expecting to keep System 2 constantly active for long periods, without planning breaks: System 2 gets tired, and when it does the brain automatically defaults to System 1. A third mistake is completely ignoring the physiological component of emotions, trying to manage them only at the level of thought, when in reality they involve chemistry, breathing and posture.

Practical example

During a long job interview, the hiring manager's System 2 tends to get tired as time passes. At that point System 1 takes over, focusing attention on likability, eloquence, clothing and appearance to quickly confirm the candidate's suitability, through confirmation bias: “they're personable, I like them, they look good.” This often leads to bad hiring decisions. An effective fix is inserting lighter questions about hobbies or personal habits during the interview, alternated with skills questions: this gives System 2 time to rest and reduces decision fatigue during the interview.

There's a detail in this example worth isolating: that first judgment (“they're personable, I like them”) doesn't stay a stand-alone opinion. It becomes a kind of filter through which later answers get read.

A weak answer, afterward, risks being seen as an exception. A strong answer, as confirmation of what had already been decided. Not because System 2 is misjudging the new information, but because System 1 has already chosen the frame, the confirmation bias named above, through which that information gets read.

The point isn't that the first impression was wrong. It's noticing that it can start shaping what you notice, before you've even realized you formed it.

You've probably already judged someone in a few seconds (likable, competent, trustworthy) only to find out later that first impression didn't hold up. That's not a character flaw: it's System 2 that, in that moment, had already handed things over to System 1.

The point isn't that you're superficial sometimes and sharp other times. It's that System 2 gets tired in predictable ways (after too many decisions, too much stress, too many hours) and when it does, the brain grabs the nearest shortcut, whatever it happens to be.

Noticing when it happens, rather than trying to be more rational in general, is what actually lets you intervene: a pause before an important decision isn't weakness; it's the same move that reduced hiring mistakes in the interview example.

Applications

Knowing how this works applies to managing selection interviews, designing work or study sessions that respect System 2's limits, managing stress and instinctive reactions in relationships, and more generally any situation where it's useful to recognize when you're deciding with real clarity and when you're simply following a mental shortcut.

Frequently asked questions

What are System 1 and System 2 of the brain?

System 1 is the one behind fast, automatic, low-energy decisions. System 2 is the one behind reflective, deliberate decisions, which requires far more energy, which is why the brain tends to avoid it when it can.

Why does the brain always favor System 1?

Because it tends to favor solutions that require less energy and less processing time. System 1 uses fewer resources, regardless of the quality of the outcome it produces.

Why is it so exhausting to change a behavior?

Because the brain, to save energy, resists sudden changes even when they're useful, relying on heuristics, mental shortcuts and biases to counter them.

What roles do the amygdala and the prefrontal cortex play?

The amygdala is one of the structures involved in the immediate emotional response to external events. The prefrontal cortex is involved in more deliberate and reflective decision-making processes, and lets you consciously choose how to respond instead of reacting automatically. Neither one, on its own, is the seat of emotion or of rationality: both are part of broader, distributed networks.

Why are breaks important during focused work?

Because System 2 gets tired with prolonged use, and when that happens the brain automatically shifts decisions over to System 1, which is faster but less accurate. Breaks let you recharge your capacity for deliberate reasoning.

Related concepts

Heuristics: the Useful Shortcuts, Cognitive Biases: Shortcuts That Become Traps, The Carriage Metaphor, What Is an Internal State, Concentration Techniques, Compulsive Buying, Impostor Syndrome, The Three Gates of Communication.

Go deeper

How the brain works, System 1 and System 2, are covered in the “Our Brain” chapter of Volume I of “The Invisible Blade”, as a foundation for understanding the following chapter on heuristics and cognitive biases.

Ing. Giovanni Ceroni

Strategic coach and mental coach. Author of The Invisible Blade – Strategic NLP series and creator of The Invisible Blade Method™.