Changing Behavior: Our Body Decides Before We Do

We’ve likely all had the experience where we tell ourselves we’re going to be focused today, disciplined today, consistent today, and then by noon, we’re scrolling, snacking, avoiding, or bargaining with ourselves. It’s a slippery slope to assume this is a character problem, a motivation problem, or a discipline problem. From a systems viewpoint, most of what we call “behavior” isn’t a choice in the way we think it is or tend to define it. It’s largely an output of our state, which is the real-time condition of our nervous system.\

The counterintuitive part is that our body often decides before we do, and if our biology isn’t on board, no amount of intention can reliably override it. The tricky part is that we tend to interpret state-driven behaviors as moral failures or character flaws. Fortunately, once we understand the mechanisms behind it, behavior change stops feeling like self-battle and starts feeling like system alignment. Still quite challenging, but at least we have a stronger foundation to build on.

*As a side-note, some of this is a bit simplified for the sake of conceptualization. Many of the systems that power human health are bi-direcitonal and interconnected, but some tend to send more traffic one way than the other.*

What Does “Behavior Comes From State” Mean?

State, in the most basic sense, is the moment-to-moment configuration of our nervous system. It’s our physiological readiness, cognitive bandwidth, emotional stability, and energetic capacity all wrapped together. Think heart rate variability, cortisol rhythms, neurotransmitter availability, sleep debt, glucose levels, thinking patterns, and levels of perceived safety (i.e. all the pieces of our life that contribute to how we feel in a given moment).

Behavior tends to emerge from that system before it is processed consciously. This is why a stressed-out brain can be impulsive, a fatigued brain avoids effort, and a well-rested nervous system feels more curious and engaged. The system’s condition shapes not only what we can do but, a lot of the time, what we want to do as well. We don’t wake up choosing cravings, avoidance, irritability, or lack of motivation—our state creates the conditions for them.

We can see this everywhere in daily life. When we’ve under-slept, decisions feel heavier. When we’re overwhelmed, tasks that normally feel doable turn intimidating. When we’re at capacity, small irritations explode. Behind every moment like this, our state, not our character, is steering the ship. With that said, over many repetitions, our state can start to become our character.

Why Willpower Fades When Biology Is Tapped Out

Willpower has been culturally inflated into a personality trait, but biologically, it’s a finite cognitive resource. As our cognitive load increases, it drops. Research on mental fatigue shows this clearly, proving that repeated decision-making, sustained focus, or emotional strain depletes neural resources in the prefrontal cortex, which is the part of the brain responsible for discipline, planning, and self-control. When the brain’s energy demands are high, its reserves are limited, and depletion masquerades as laziness. 

This is also why “just push harder” fails if not timed perfectly. Willpower works when the system is balanced but collapses when the system is taxed. It’s easy to interpret this collapse as weakness when it’s really the brain protecting itself. A depleted prefrontal cortex cannot out-discipline a body experiencing high cortisol, low glucose, collapsing dopamine, or a nervous system in threat mode.

The lesson isn’t that willpower is useless; it’s that it’s a terrible primary strategy. It’s the emergency parachute, not the daily driver.

Why Stress Makes Habit Change Feel Impossible

Stress is a physiological state that reorganizes our priorities. The body shifts from exploration to protection, from long-term goals to short-term survival. We can feel this shift in everything from cravings to attention. Chronic load elevates cortisol and erodes resilience, reshaping cognition into narrow, threat-sensitive patterns. When stress hijacks the system, the brain becomes less flexible, less curious, and less willing to take on new behaviors.

This is why stressed people usually procrastinate more, not because they’re necessarily irresponsible, but because a sympathetic-dominant state literally suppresses planning and execution circuits. The nervous system interprets effort as threat and redirects energy elsewhere. The same person, in a more regulated state, usually completes tasks with ease. 

The key behind all of this is that state dictates capacity, and capacity dictates behavior. If we want to change our behavior, we need to dial in state first, not the other way around.

Fatigue is a Filter

When we’re drained, our world shrinks. Options feel fewer and demands feel larger. The same concept applies to habits. A fatigued nervous system becomes selective. It preserves energy by steering us away from anything that feels cognitively expensive, even if it’s something we want to do. Habits that are already established become the path of least resistance, and changing old habits or establishing new ones become energetically out of reach.

It’s not personal. It’s physics. Any system low on resources defaults to protective, energy efficient patterns. Those patterns often show up as avoidance, distraction, or impulsivity. When we look at behavior through this lens, it stops looking like sabotage and starts looking like conservation.

The Myth of “Try Harder”

A common approach is to blame inconsistency on a lack of motivation, but motivation itself is state-dependent. Dopamine, one of the neurotransmitters largely behind motivation, fluctuates based on energy, mood, stress, sleep, and other factors. Chronic stress lowers baseline dopamine, cognitive fatigue flattens dopamine spikes, and low dopamine makes everything feel heavier.

This is why an overworked person can want to change but still feel unable to start. It’s why people are more optimistic after a good night’s sleep and more pessimistic after chronic load. The system decides how possible something feels long before it becomes a conscious attitude.

This also ties closely to identity. Repetition builds identity, but identity doesn’t only shape behavior. The reverse is also true. A chronically depleted state can distort identity. “I’m inconsistent,” “I’m not disciplined,” “I can’t stick to anything,” are oftentimes state-dependent conclusions, not truths, but repeated enough times, and they truly start to feel like a part of us.

The Real Key to Changing Behavior

A regulated nervous system is a learning nervous system. A stressed or fatigued nervous system is a protective one. This is why new habits can seem nearly impossible to establish when life feels chaotic. The body simply doesn’t perceive enough safety to invest in the future.

Social safety, through oxytocin, nervous system synchrony, and reduced cortisol, expands our cognitive bandwidth. Just being around people we trust and enjoy spending time with can have a massive, positive impact when changing behavior. When we feel safe, new behaviors stop feeling threatening to the system. They require less fight, less force, and less mental gymnastics. Safety is not a luxury. It’s the prerequisite for change.

So How Do You Actually Change Behavior?

This doesn’t mean we wait for perfect conditions. It means we create micro-conditions that shift the body toward readiness. The simplest lever is regulation, meaning anything that brings our system closer to calm focus. Sleep, nutrition, movement, daylight, stillness, co-regulated connection, moments of awe are all levers we can pull. These aren’t nice-to-haves; they’re the biological foundation that make new behaviors possible.

Once the system is stable, behavior change stops feeling like a fight and starts feeling like alignment. The friction drops. Tasks feel lighter. Discipline stops being an uphill battle. We’re no longer trying to override the system, rather, we’re letting the system work for us.

In the End, Behavior Is Not a Measure of Who We Are

Behavior is almost always a reflection of the state we’re in.

When we shift state, everything downstream shifts with it, including motivation, discipline, choices, capacity, desire, etc. Understanding this removes the shame that often accompanies change. It reframes the entire process. We stop asking, “What’s wrong with me?” and start asking, “What does my system need to support this behavior?”

This is the heart of performance health. Our body is responding exactly as a well-designed survival system would, and once we learn to work with that system instead of against it, behavior change stops being a battle of will and becomes a matter of biology.

References

1. Hockey, G. R. J. (2013). The Psychology of Fatigue: Work, Effort, and Control. Cambridge University Press.

2. Boksem, M. A. S., & Tops, M. (2008). Mental fatigue: Costs and benefits. Brain Research Reviews.

3. McEwen, B. S., & Gianaros, P. J. (2011). Stress- and allostasis-induced brain plasticity. Annual Review of Medicine.

4. Arnsten, A. F. T. (2009). Stress signaling pathways that impair prefrontal cortex function. Nature Reviews Neuroscience.

5. Marcora, S. M., et al. (2009). Mental fatigue impairs physical performance in humans. Medicine & Science in Sports & Exercise.