If we were to draw our autonomic nervous system as a line on a chart that moves up and down in its level of activation, it would look like a wavy line that is constantly moving as it responds to our daily events and stressors. 

On this chart, some experts like to call the green zone the "window of tolerance". When you’re within this green zone ‘window’ your nervous system is  flexible and adaptive, reacting and responding to the events that occur in your daily life while still staying regulated. This means you are able to tolerate the emotions and experiences that happen in your daily life, even if they're difficult or stressful. 

As we’ve already learnt, if something happens that’s too overwhelming or stressful, it can signal a danger response in your nervous system that can temporarily push you outside your window of tolerance and into the yellow or red zones. Even though this experience at the time may feel unmanageable or overwhelming, with healthy nervous system regulation we're able to return back to the green zone after this event has passed, and can continue to cope with daily events like before. 

However, sometimes when we are exposed to a lot of chronic or continued stress, are feeling unsupported, or are facing other difficult or traumatic situations for a long period of time, our ‘window of tolerance’ can start to get smaller. This can mean that things that you were able to cope with or stay in the green zone for in the past can suddenly be outside your window of tolerance - causing a danger or shutdown response in the nervous system. 

Have you ever had a really tough day or week, where everything seemed to go wrong, and suddenly something little like dropping your wallet or keys makes you fall apart? This is because our window of tolerance has shrunk. 

With a smaller window of tolerance, it can be a bit harder to access the regulated state of the green zone. Our nervous system can become dysregulated - where we find ourselves being stuck in the yellow or red zones more easily or for longer periods of time. 

Being stuck in constant states of anxiety, panic, overwhelm or depression can cause us to try to cope in ways that maybe aren’t so healthy or appropriate. This makes sense if our access to the calming and regulating state of the green zone isn’t easily accessible to us because of how small our window is. We’ll talk more about coping behaviours in another module. 

It's important to know that no matter how small our window of tolerance might be - we can widen it. There are many tools, techniques and coping strategies that can help you learn to regulate yourself and widen this window, and restore a sense of calm and stability within your nervous system.  By widening our window of tolerance, we can learn how to stay regulated and experience "enough", rather than too much or too little, in response to things that might have been dysregulating in the past.