In March 2020, a friend of mine sold everything.
She is not foolish. She has a master’s degree, runs a team of twelve, and could explain compound interest to you over coffee without notes. For years she had done everything right: a steady savings rate, a diversified portfolio, an emergency fund sitting quietly in the bank. On paper she was the model investor.
Then the market fell 30% in a month, the news used the word “unprecedented” every nine minutes, and one Tuesday evening she logged in and sold all of it. Locked in the loss. Sat in cash through the recovery. By the time she felt calm enough to buy back, prices were higher than when she sold.
She knew, the entire time, that selling in a panic is the classic mistake. She could have told you so. And she did it anyway.
This series is about why.
The thing intelligence does not fix
We tend to assume bad money decisions come from not knowing enough. Learn the math, the theory goes, and the behaviour follows. So we read the books, build the spreadsheets, understand risk and diversification, and feel prepared.
Then a real decision arrives, with real money and real fear attached, and the knowledge sits uselessly in one part of the brain while a much older part does something else entirely.
The uncomfortable truth that behavioural science has spent fifty years documenting is this: knowing the right thing and doing the right thing are different skills. They live in different places. And under pressure, the one that wins is usually not the one holding the spreadsheet.
Two systems sharing one head
The psychologist Daniel Kahneman won a Nobel Prize for an idea he could describe in two sentences. Your mind runs two systems.
System 1 is fast. It is automatic, effortless, emotional, always on. It recognises a friend’s face, flinches at a loud noise, and senses, instantly, that a deal is “too good to miss.” It does not calculate. It reacts.
System 2 is slow. It is deliberate, effortful, logical, and lazy. It multiplies 17 by 24, compares two loans, decides whether an investment actually fits your plan. It is accurate when it shows up. The problem is that it would rather not show up at all, because thinking hard is genuinely tiring, so the brain hands as much as possible to System 1.
My friend in March 2020 was not stupid. Her System 2 knew exactly what selling in a panic does. But the fear of watching her net worth fall was a System 1 event, and System 1 acted first. System 2 arrived a few minutes later, looked at what had happened, and did what System 2 usually does in these moments: it invented a sensible-sounding reason. “I was reducing my exposure to uncertainty.” A justification, written after the fact, for a decision that was already made.
A brain built for a different problem
Here is the deeper reason this keeps happening. The brain you carry around was shaped over hundreds of thousands of years by one job: surviving long enough to reproduce. Money, in any form resembling today’s, is a few thousand years old. Index funds and retirement accounts are decades old.
The instincts that kept your ancestors alive are spectacularly wrong for modern money:
- React instantly to threat. Brilliant for a rustle in the grass. Disastrous for a falling market, where the instinct to flee locks in the loss.
- Follow the group. Safe when the tribe runs from danger. Dangerous when the crowd is inflating a bubble.
- Value what is in front of you. Sensible when food might rot or be stolen. Ruinous when it means spending today what your future self needed for retirement.
- Avoid loss above all. Sound when a loss meant starvation. Costly when it means refusing to sell a bad investment because admitting the mistake hurts.
None of these are character flaws. They are the standard equipment, working exactly as designed, on a problem they were never designed for. Calling yourself undisciplined misunderstands the situation. You are running survival software on a wealth-building task.
Why awareness alone will not save you
The natural response is: fine, now that I know, I will just be more careful.
It mostly does not work on its own. One of the most humbling themes in the field is that knowing about a bias reduces it far less than you would hope. The researchers who discovered these effects fall for them too, and say so openly. Awareness is necessary, but it is nowhere near sufficient, because the biases operate below the level where “trying harder” reaches.
You cannot out-discipline a system that acts before discipline wakes up.
What does work is design. The brain can change slowly, through years of practice, and neuroplasticity is real. But you cannot count on rewiring a fast, evolved instinct in the few seconds of a real money decision, while the fear is live. So the practical move is not to retrain the brain in the moment but to rearrange the situations it operates in, so the right decision is the automatic one and the wrong decision is the one you would have to go out of your way to make.
A few examples make the idea concrete. When saving happens automatically, willpower never has to be summoned. When the portfolio is reviewed quarterly rather than checked daily, there are simply fewer heated moments to survive. When the rules are decided in advance, in a calm room, a stressful day only has to follow a plan rather than invent one. None of these ask you to feel differently. They quietly arrange things so the feeling matters less. The final post in this series gathers these into a full toolkit; for now, the point is just that the lever is the situation, not the willpower.
That is the whole strategy of this series, stated once up front: stop fighting your brain and start designing around it.
The opponents you are about to meet
The rest of this series introduces the specific patterns, one at a time. Each is a predictable way System 1 hijacks a money decision, and each has a known countermeasure. You will meet:
- Loss aversion, the reason a loss hurts roughly twice as much as the same gain feels good, and why that makes people sell at exactly the wrong time.
- Mental accounting, the trick of treating money differently depending on the label on it, even though every euro is identical.
- Present bias, the constant pull of now over later that quietly starves your future self.
- Overconfidence, the widespread belief that you are an above-average investor, which cannot be true for most people at once.
- Framing and anchoring, where the same decision becomes a different decision depending on how it is described.
- Herd behaviour and FOMO, the ancient pull to do what everyone else is doing, which builds bubbles and crashes alike.
- Narrative economics, the way a good story can move markets more than any fundamental.
- Money scripts, the unconscious beliefs about money you absorbed in childhood and still run on autopilot.
And finally, a capstone: how to assemble everything into a financial life that quietly defeats your own worst instincts.
What you can do
You do not need to act on all of this yet. The biases come one post at a time. But three things are worth carrying in from the start:
- Stop blaming intelligence. When you or someone you know makes a money mistake, the question is not “how could they be so dumb.” It is “which fast instinct beat the slow plan.” That reframing is more accurate and far more useful.
- Notice the heated moments. A market drop, a hot tip, a ticking-clock offer, a purchase that suddenly feels urgent: these are System 1 events. The feeling of urgency is itself the warning sign.
- Trust systems over willpower. Anything important that depends on you being calm and disciplined in a stressful moment is likely to fail eventually. Anything important that happens automatically is far more likely to hold.
My friend who sold in March 2020 changed one thing afterward. She set her investments to buy automatically every month and deleted the app from her phone. She has not made the same mistake since, not because she became smarter, but because she stopped relying on being smart in the worst possible moment.
The first and most expensive of those instincts is the one that drove her to sell: the fact that losses hurt far more than gains feel good. That is loss aversion, and it is where we go next.