The Biology of Leadership · Issue 05 · Sent to subscribers 19 August 2026
It’s 8:30pm on a Wednesday. You finished work at five, in the sense that you stopped. The project didn’t. There’s more in it, there’s always more in it, and you’d quite like to be ahead of it by morning.
The house is quiet, so you open the laptop for one more thing. Forty minutes later, you’re still there. The tiredness you could feel at five hasn’t gone anywhere. You’ve just become very good at ignoring it.
I keep hearing versions of this in the interviews, particularly from people who are deeply connected to what they do. The work matters to them. They feel useful doing it. They are building something, solving something, leading something they genuinely care about.
And that creates an interesting predicament.
The fuel and the fire are often the same thing.
Purpose can give you extraordinary energy. It can help you tolerate pressure, persist through difficulty and find another gear when other people might stop. But those same qualities can make depletion harder to recognise, because the work itself keeps giving something back.
That, I think, is where passion becomes biologically interesting.
Fuel: meaning, energy, persistence, focus, progress.
Fire: overextension, ignored fatigue, reduced recovery, difficulty stopping, identity tied to output.
The same thing that helps you keep going can make it harder to know when to stop.
The insight this week
The biology of passion
We tend to assume that motivation, enjoyment and capacity move together. If I still want to do the work, surely I must still have something left to give it.
But the brain doesn’t organise reward quite that neatly.
The system that makes you want something runs separately from the one that tracks whether you can afford it. Dopamine is heavily involved in pursuit. It helps make the next problem salient, interesting and worth going after. It keeps attention fixed on the thing that matters and makes opening the laptop again at 8:30pm feel perfectly reasonable.
Motivation is not a recovery signal.
That matters because your brain does not require you to feel recovered before it allows you to feel interested.
You can carry accumulated fatigue and still get a hit of energy from solving the next problem. You can be underslept and still feel completely absorbed in a conversation that matters. You can be running low and still feel pulled towards work that gives you purpose, progress or a sense of usefulness.
So the fact that you still want to work tells you surprisingly little about whether your body has recovered enough to keep doing it well.
Circuit one, wanting. “I want to keep going.” Dopamine and pursuit, interest, anticipation, problem-solving, progress.
Circuit two, capacity. “I have enough physiological resource to keep going well.” Sleep, recovery, energy availability, stress load, physical and cognitive fatigue.
Neither circuit checks the other.
For someone doing work they don’t particularly care about, fatigue may eventually win the argument. But when the work itself is rewarding, purposeful and bound up with identity, the wanting signal has something powerful to keep feeding it.
This is why I think purpose is such an interesting leadership variable.
We usually talk about purpose as protective, and often it is. Purpose helps people tolerate difficulty. It can create resilience. It gives effort a reason.
But it can also blur the boundary between what is energising you and what is consuming you.
Hence why the fuel and the fire are often the same thing.
So why does anyone stop?
Our bodies have very obvious versions of stopping signals elsewhere.
Eating is one. As food enters the mouth and gut, sensory, mechanical and nutrient feedback begin contributing to the process that eventually brings the meal to an end. Thirst has its own feedback systems. Physical exertion produces increasingly difficult-to-ignore signals as well.
There are physiological brakes.
Interesting work is different.
There isn’t a task-specific satiety system counting the problems you’ve solved and deciding that seven is enough for today. No useful hormone rises at 6:17pm and tells you that you’ve been productive enough.
Fatigue can signal. Stress can signal. Sleepiness can signal.
But none of those necessarily switches off your desire to keep pursuing something your brain still finds rewarding.
The body can be saying “enough” while the motivational system is still saying “more.”
And it helps explain why passion itself probably isn’t the problem.
The more interesting question is what your passion is carrying.
Robert Vallerand’s work distinguishes between two forms of passion that can look remarkably similar from the outside.
Harmonious passion is integrated into the rest of your life. You love the work. It matters enormously. But it sits alongside other parts of who you are, and you can still put it down.
Obsessive passion becomes more tightly attached to identity. The work is no longer simply something you care deeply about. It starts carrying part of your sense of who you are.
Both can produce long hours. Both can produce exceptional effort. Both can look like commitment.
The difference is whether you still feel free to stop.
If work is simultaneously giving you energy, meaning, progress, identity and reward, then stopping is no longer a simple decision about whether you are tired.
From the interviews
One purpose-led chief executive told me she greets a particular landmark on her drive to work. The same one, every morning.
If she drives past without noticing it, or forgets to say good morning, she knows she is too far inside her own head. It is one of the ways she recognises that she is becoming overwhelmed.
It created a feedback signal that her working life wasn’t going to otherwise offer very loudly. A small external cue that told her something about her internal state.
But there is another part of her story that bugged me.
She is one of the most self-aware leaders I’ve spoken to. She notices what is happening in her body. She can describe depletion while it is happening. She has rituals that help her recognise when things are beginning to slide.
And she still hit a wall.
By November, in her words, there was nothing left in the can. What eventually brought her back was four weeks of enforced stop.
Not better insight. Actually stopping.
We talk a lot about awareness. Notice the signs. Listen to your body. Catch things earlier. All good advice.
But knowing you are depleted is not the same as being able to stop.
Especially when the thing depleting you is also giving you meaning, stimulation, progress and a fairly substantial part of your identity.
The question I keep coming back to
Could I put this down for a week and still feel like myself?
Not, could I physically stop working for a week? Most people could. But if the work disappeared for seven days, would you still know who you were without it?
If the answer is yes, your passion probably has somewhere to rest. The long hours may be a season rather than a shape.
If the answer is no, I don’t think the answer is to care less. I’ve never found “care less” particularly useful advice for people who have found work worth caring about.
I think the more interesting question is what else in your life carries enough weight to remind you of who you are when you’re not working. Relationships. Family. Movement. Places. Parts of your life that matter despite having no measurable output attached to them.
And there is another question underneath that one: when I still want to keep going, what other signal tells me whether I actually should?
Because next Wednesday at 8:30pm, the laptop will still be there. The project will still have more in it, and the part of you that wants to keep going will probably be just as loud.
You wouldn’t necessarily want that drive to disappear. That drive may be part of what makes you excellent at what you do.
The challenge is making sure it isn’t the only signal you can hear.
The other signal
The Capacity Wheel is a read on which way your wheel is turning, and on how much you have to spend before you ask yourself to spend it. About three minutes. It is a mirror, not an assessment.
Which way is your wheel turning?
Wanting to keep going and being able to keep going well are two different signals, and only one of them announces itself.
This is Issue 05 of The Biology of Leadership, a weekly note written while I work on Beacon, a book on the biology of leadership. Subscribe here to get each issue a day before it appears on the journal.