The stress response is our instinctive response to perceived danger, whether it is real or imagined. People will perceive different dangers, for some people what they experience as a danger may be perceived by others as quite safe. For example, I might see a wasp as a danger, someone else might be quite relaxed about it. This might be to do with their disposition, or it might be to do with their experiences.
When we perceive this danger, we typically react with the Fight, Flight or Freeze response. Most people have one of these as a default response. Our Sympathetic Nervous System prepares us for fight or flight by producing adrenaline, nor-adrenaline and cortisol which immediately raise our heart rate and blood pressure, increase muscle tension and sensory alertness and makes blood glucose available. This means we are ready for a physical response to the danger. We might attack the source of the danger, in some way, perhaps verbally or physically (Fight) or we may run away from it (Flight). The changes in our body enable us to do these things.
If the threat is perceived as inescapable then the Parasympathetic Nervous system over-rides these changes and we experience the freeze response: immobility, numbness and dissociation. In animals this can be seen as playing dead.
All these responses happen without conscious thought, they are involuntary and while this is happening, we tend to be totally focussed on the threat, and our thinking is probably not very clear or rational.
Once we perceive that the threat has gone then they body readjusts, there is a decrease in the stress hormones, our muscles start to relax, heart rate and blood pressure reduce, and our minds become clearer. There may be some self-criticism about the way that we responded, although in truth it was probably outside of our immediate control. It may then be that we return to normal.
However sometimes we may need to work on resolving our stress response. This might include burning off excess tension through physical activity or giving our body and mind a feeling of safety and security. We may engage in activities that give us a feeling of comfort and control some of which have long term negative effects, e.g. lighting a cigarette, drinking alcohol to steady our nerves, overeating etc. Other ways of feeling comfort and control may be much more beneficial, taking a bath, going for a walk etc.
It may be that we need to therapeutic help to change our response to, or perception of, these danger signals and we may need help to resolve the experience, particularly in traumatic situations and deal with any guilt or shame.
Ongoing long-term stress can lead to a wide range of difficulties: physiological, cognitive, emotional, behavioural, relational and Identity and therapy can help here.