The framing itself is the error. What follows is the corrected version. You have been told, in various forms, that you are “too much” or “too sensitive” or, conversely, that you are “closed off” and “hard to reach.” Perhaps both, in different relationships or different seasons of your life.
What is almost never named in those conversations is that what looks like a character trait — emotional volatility or its opposite, emotional flatness — often reflects the nervous system’s current capacity to process experience. And capacity is not fixed.
This distinction matters enormously. If emotional range is a character flaw, then change requires becoming a different kind of person. If it is a nervous system state, change requires something much more practical: expanding the window.
What the Window of Tolerance Actually Is
The window of tolerance is a clinical concept first articulated by Daniel Siegel (1999) and later developed within the somatic and trauma therapy traditions by Pat Ogden, Janina Fisher, and others. It describes the optimal zone of nervous system arousal within which a person can process experience — including emotional experience, relational friction, and stress — without becoming overwhelmed or shutting down.
Within this window, the prefrontal cortex remains online. The person can think, feel, and respond. They have access to nuance, to self-reflection, and to choice.
Outside this window, in either direction, the situation changes fundamentally.
Hyperarousal — the upper edge — is the state of too much activation: anxiety, panic, rage, flood. The sympathetic nervous system has taken over the show. The prefrontal cortex goes partially offline. The capacity for reflective thought narrows. Reactivity increases. This is the person who escalates in conflict, who cannot stop the spiral once it starts, whose body seems to be responding to a threat much larger than the one actually present.
Hypoarousal — the lower edge — is the state of too little activation: shutdown, dissociation, flatness, numbness, the sense of watching yourself from a slight distance. The dorsal vagal system has taken over. The person is technically present but experientially unreachable — by themselves and by others. This is the person who goes silent in conflict, who cannot access what they feel, who describes a kind of blankness where emotion should be.
Both hyperarousal and hypoarousal look like personality. They are nervous system states.
Why Trauma Narrows the Window
A history of chronic stress, early adverse experience, or trauma — including the diffuse, difficult-to-name kind that doesn’t meet clinical trauma criteria but leaves its mark on the body nonetheless — consistently narrows the window of tolerance.
The mechanism is not mysterious. Repeated activation of the stress response, particularly in early development when the nervous system is still calibrating its threat baseline, teaches the system that the world is more dangerous than it is safe. The autonomic nervous system adjusts accordingly: it becomes faster to activate, more vigilant, less able to return to rest. The window of what is manageable without tipping into over- or underactivation becomes narrower.
This calibration is not pathology. It is the nervous system doing exactly what it evolved to do: learning from experience and adjusting its sensitivity to threat based on the environment it has inhabited.
The difficulty is that the environment changes — the original source of threat is no longer present — but the calibration does not automatically update. The nervous system continues predicting danger at the rate it learned to, in a context that no longer requires it.
Polyvagal theory (Porges, 1994, 2011) describes this in terms of neuroception — the nervous system’s continuous, largely unconscious scanning for threat or safety cues in the environment. Trauma history shifts the neuroception threshold, so that cues which would register as neutral or safe to a non-traumatised nervous system are read as ambiguous or threatening. The system responds accordingly.
In practical terms: the person is not “overreacting.” Their nervous system is reacting accurately to a prediction built from real history. The problem is not the reaction — it is the outdated threat model generating it.
The High-Functioning Presentation
One of the complicating factors in this work is that a narrow window of tolerance is frequently invisible from the outside — and often invisible to the person themselves until a threshold is crossed.
The high-functioning presentation is common: someone who is performing at a high level professionally, managing relationships, maintaining the appearance of stability — while running a constant background process of vigilance, social scanning, and effortful self-regulation. The energy required to maintain functioning within a narrow window is significant. It is drawn from somewhere.
Eventually, it is drawn from everywhere.
The collapse that follows — the burnout, the relational rupture, the anxiety that can no longer be managed, the numbness that settles in — is often diagnosed as the problem. It is, more accurately, the bill from years of operating with a window that was never addressed.
The body is not failing. It has been compensating for a very long time, and it has run out of resources for doing so.
What Actually Expands the Window
The window of tolerance does not expand through insight, though insight helps create the conditions for the work. It expands through somatic experience — through the repeated experience of moving to the edge of the window and returning to centre, with support.
Several evidence-informed mechanisms are relevant here:
Vagal tone. Heart rate variability (HRV) — the variation in time between heartbeats — is a measurable marker of vagal tone, the capacity of the parasympathetic nervous system to modulate the stress response. Higher HRV is associated with greater emotional regulation capacity, better recovery from stress, and a wider functional window. Vagal tone can be increased through specific practices — slow diaphragmatic breathing (particularly with extended exhalation), humming, cold exposure, and somatic movement. These are not relaxation techniques. They are direct inputs to the autonomic nervous system.
Co-regulation. The nervous system is a relational system. It learns safety and threat in relationship to other nervous systems, particularly in early development. This means that healing — the genuine recalibration of the threat baseline — also happens relationally. A regulated nervous system in the room (a therapist, a skilled practitioner, a safe attachment relationship) creates the neurobiological conditions for the dysregulated system to down-regulate. This is not a metaphor. It is the social engagement system (ventral vagal) doing its actual job.
Titration. Working with activation in small, tolerable doses — approaching the edge of the window and returning to centre, repeatedly — trains the nervous system to expand its capacity. The technical term is pendulation (Levine). The principle is exposure with return to resource.
Somatic anchoring. Grounding practices — orientating to the physical environment, noticing points of contact with the floor or chair, using breath as an anchor — activate the ventral vagal system and support the nervous system in registering the present moment as different from the threat history.
None of this is complicated. All of it requires consistency and, in most cases, guidance — because the person with the narrowest window is also the one for whom self-directed practice is most difficult when activated.
What is the window of tolerance?
The window of tolerance (Siegel, 1999) describes the zone of arousal in which a person can function — receive information, process emotion, and stay present — without tipping into hyperarousal (fight/flight) or hypoarousal (shutdown/freeze). It is not fixed. It can be widened.
Why does my window of tolerance feel so narrow?
Repeated or unresolved stress and trauma narrow the window over time. The nervous system — calibrated for the level of threat encountered historically — becomes less able to tolerate emotional activation before tipping into hyperarousal or collapse.
What widens the window of tolerance?
Regulated somatic experience — repeated, dosed exposure to activation that resolves — expands the window over time. Polyvagal-informed work, somatic therapy, and safe relational experience all contribute to genuine expansion, not just management.
The Question Worth Asking
If you have been living in a narrow window — managing, functioning, holding things together — the question is not what is wrong with you. There is nothing wrong with you.
The question is: what would it cost you to stay here? And what might become available if the window were wider?
More regulatory capacity is not just a clinical outcome. It is access to more of your own life: richer relational experience, cleaner decision-making, sustained creative output, the capacity to be present in the moments that matter instead of managing them from behind glass.
If you are unsure which layer of this work is most relevant to you right now, The Insight-Integration Gap Check is a brief self-assessment designed to give you a clear read.
→ Download the Gap Check — free
If the window of tolerance is clearly where the work needs to happen, the Alchemical Threshold — a 3-session container — is specifically designed for this level of somatic, nervous system-led work.
→ Explore the Alchemical Threshold
References
- Siegel DJ. (1999). The Developing Mind: How Relationships and the Brain Interact to Shape Who We Are. Guilford Press.
- Ogden P, Minton K, Pain C. (2006). Trauma and the Body: A Sensorimotor Approach to Psychotherapy. W.W. Norton.
- Porges SW. (1994). The polyvagal theory: Phylogenetic substrates of a social nervous system. International Journal of Psychophysiology, 42(2), 123–146. https://doi.org/10.1016/S0167-8760(01)00162-3
- Porges SW. (2011). The Polyvagal Theory: Neurophysiological Foundations of Emotions, Attachment, Communication, and Self-Regulation. W.W. Norton.
- Levine PA. (2010). In an Unspoken Voice: How the Body Releases Trauma and Restores Goodness. North Atlantic Books.
- Thayer JF, Åhs F, Fredrikson M, Sollers JJ, Wager TD. (2012). A meta-analysis of heart rate variability and neuroimaging studies. Neuroscience & Biobehavioral Reviews, 36(2), 747–756. https://doi.org/10.1016/j.neubiorev.2011.11.009
Rosa F. Brissos, PhD is a biochemist and holistic therapist specialising in nervous system regulation, somatic trauma work, and psychedelic preparation and integration. Based in Portugal. Working internationally.
