Your Nervous System’s Best Investment — Part 2 of 4
By Eva Selhub, MD
It is Sunday evening, but it feels like you are already in Monday. The week ahead is running through your mind — the meetings, the decisions, the people who need things from you. Your body might be in the room, but your attention lies somewhere else entirely, scanning, preparing, and possibly bracing. For many high achievers, this has become so familiar it no longer registers as stress. It is simply part of the game…Until it no longer is. Until something starts to feel off or break.
And for the most part, up until now, this pattern has worked. It is precisely why you have gotten where you are. The goal-oriented, forward-driving lifestyle that keeps the nervous system in a state of constant mobilization is what has gotten things done, closed deals, built companies, and in some cases saved lives. It has worked. It continues to work. The question — one you may or may not have asked yourself — is at what cost.
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The Nervous System Was Designed for Rhythm
The nervous system was designed for rhythm. Activation and recovery. Mobilization and restoration. The stress response was never meant to run continuously — it was designed to switch on, resolve the challenge, and switch off again, returning the body to the state where growth, repair and replenishment can occur. When that oscillation is intact, the system is resilient. It can absorb enormous demands, recover fully, and return stronger. This is what optimal performance actually looks like at a biological level — the fluid movement between effort and restoration, between activation and rest.
When that oscillation is disrupted — when activation never fully resolves because the next goal/problem/demand is always waiting— the body begins accumulating what Bruce McEwen called allostatic load: the biological cost of chronic stress that never fully turns off (McEwen, Annals of the New York Academy of Sciences, 1998). The body can carry the stress load for a remarkably long time. High performers are often exceptional at it. But the capacity is not unlimited, and at some point, the system –mind, body, spirit—will shift from adaptability, flexibility and flow to rigidity and pathology. It may show up as disrupted sleep, reduced recovery between efforts, inflammation that doesn’t fully resolve, more irritability, elevated blood glucose markers, or the particular quality of exhaustion that rest doesn’t touch.
One of the most precise ways to measure this physiologically is through heart rate variability (HRV) — the variation in time between heartbeats that reflects the nervous system’s capacity to shift fluidly between activation and recovery. High HRV indicates a system with genuine flexibility, one that can mobilize fully when demanded and restore fully when it doesn’t need to. Research consistently links low HRV to burnout, cardiovascular disease, impaired decision making and reduced emotional regulation (Arakaki et al., Frontiers in Neuroscience, 2023) (Järvelin-Pasanen et al., ScienceDirect, 2016). In measurable biological terms, it is what chronic allostatic load looks like from the inside — a nervous system stuck in activation, unable to downshift regardless of the circumstances.
Left unaddressed, the physiological consequences accumulate. The cardiovascular system sustains elevated cortisol and adrenaline levels that were designed to be temporary. The immune system, which requires the parasympathetic recovery state to function well, becomes dysregulated — more inflammatory, less discriminating. Metabolic function deteriorates. Sleep architecture fragments. And critically for anyone whose performance depends on it, the prefrontal cortex — the seat of complex thinking, nuanced judgment and long-range planning — progressively loses access to its full capacity as the amygdala dominates. Decision making narrows. Emotional reactivity increases. The very cognitive resources that produced the achievement begin to erode under the weight of the system driving it.
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Restoration, Flow and the Love Response®
The beauty of the human design is that it is amenable to change and healing. It is has an inherent biology meant for restoration.
Herbert Benson demonstrated decades ago that the relaxation response — a state of deep physiological quiet produced through meditative focus — reverses the stress cascade measurably: heart rate slows, cortisol drops, immune function recovers, and the prefrontal cortex regains access to its full capacity (Benson & Klipper, The Relaxation Response, 1975). The system, in other words, given the right conditions, knows how to restore itself. Practitioners of Zen, meditation and contemplative traditions have understood this for centuries — that within the stillness, something reorganizes. The mind clears. Perspective returns. The body remembers how to regulate itself when the noise is removed.
Flow — the state of optimal engagement described by Csikszentmihalyi — takes this a step further. In flow, the nervous system achieves something distinct from either rest or stress: a state of calibrated, effortless engagement in which performance is high, self-consciousness recedes, and time distorts. Recent research measuring the physiology of flow found a U-shaped relationship between flow and heart rate variability — flow represents its own autonomic state, neither the high arousal of stress nor the low arousal of rest, but something in between that the nervous system settles into when challenge and skill are perfectly matched (Physiological Assessment of Flow, Scientific Reports, 2025). This is the state athletes call being in the zone. It is also the state in which the amygdala quiets, the prefrontal cortex operates at its most fluid, and decisions are made with a clarity that stress never allows.
The Love Response® makes both of these states more accessible and more sustainable. When the physiological state of deep restoration is infused with love — through genuine connection to another person, to nature, to something larger than the self, or to an inner sense of safety, belonging and awe — the body does not simply rest. It heals at a level that rest alone may not fully reach. Oxytocin actively down-regulates the HPA stress cascade. Endorphins and the opioid system provide the stabilizing signal of relief — the felt sense that balance has been restored, that the challenge has resolved, that the system can finally stop reaching. The dopaminergic reward system encodes this state as worth returning to, and the nervous system begins to learn a new pattern — one in which restoration through connection becomes as available and as habitual as the drive that got you here. And because the nervous system is no longer running the chronic low-grade threat response in the background, flow becomes easier to access, clarity returns more readily, and the performance that drove you to succeed operates from a more stable biological foundation.
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So What Does This Mean in Practical Terms?
The first step is awareness — not as an abstract concept, but as a practice of returning attention to what the body is already communicating. Every sense you have — what you see, hear, feel, taste, smell — is constantly feeding information about your internal and external world into the nervous system. Intuition, that felt sense of knowing that arrives before you can explain it, is part of that same system. The body is always speaking.
The problem is that a life organized around goals and outcomes trains attention in one direction — forward, toward what needs to happen next. The signals coming through the senses, the subtle physical communications about how the system is actually doing, get filtered out as irrelevant to the task at hand. The tension in your jaw has been there so long, it no longer registers. Or perhaps that constriction in your chest that has been overridden so many times it has never been fully noticed. And that fatigue that you may have treated with drinking more coffee and pushing harder. The nervous system is speaking constantly through the body’s signals, but if you are like most, you have paid more attention to the goals rather than the signs.
The body whispers before it screams. What begins as a quiet signal — a quality of sleep that has shifted, a flatness where energy used to be, a low-grade irritability that arrives without a clear cause — can become, over time, the louder language of chronic illness, burnout or breakdown. By then the system has been trying to communicate for a long time.
The practice of witnessing physiology — of turning attention toward bodily sensation, toward the breath, toward what the senses are actually reporting in this moment — is the foundation of everything that follows. Mindfulness and meditation traditions have understood this for centuries. The neuroscience now confirms what practitioners have always known. Neuroimaging studies show that regular mindfulness practice produces measurable structural changes in the brain: increased cortical thickness in the prefrontal cortex, reduced amygdala reactivity to emotional stimuli, and strengthened connectivity between the prefrontal cortex and amygdala — meaning the brain’s capacity for regulation over its own threat response literally grows (Kral et al., NeuroImage, 2018). A 2024 systematic review confirmed that mindfulness practice is associated with increased gray matter in regions tied to self-regulation and executive function, and reduced amygdala volume — the brain’s fear center becoming less dominant (Biomedicines, 2024). In long-term meditators, emotional regulation becomes less effortful over time — the nervous system learns to process experience without being hijacked by it, and that capacity for resilience becomes structural, not just behavioral.
This quality of present, non-judgmental attention to the body’s signals is itself a regulatory act. It begins to shift the nervous system out of the chronic forward lean of threat anticipation and into the present moment, where restoration is actually possible.
HRV tracking and wearable technology can add another layer to this awareness — offering an objective, measurable window into where the nervous system’s capacity for recovery actually stands. For those drawn to data, it is a valuable tool. A consistent pattern of low or declining HRV is the nervous system communicating in numbers what the body is already communicating in sensation.
The next piece in this series goes into the Love Response® directly — the three pillars of social love, self love and spiritual love that form the biological infrastructure of resilience, and what building each one actually looks like in a life that has been organized primarily around performance and achievement. For those who have built their lives on forward momentum, some of what follows may be counterintuitive. All of it is grounded in the same biology that got you here.
