Stress is widely observable in the animal kingdom. It is a physiological response to a threat - typically a physical threat such as a predator. Its job is to prepare the body for action in order to stay safe, usually by means of one of two methods: fight or flight.

This is why stress has the effect it does. Your heart rate rises, you breathe faster, start to sweat and possibly feel nauseous (under extreme stress, some people actually are sick). This is because your body is making sure that the muscles have all the oxygen they need for the action that will get you out of danger. The blood is directed away from the extremities and non-essential systems like the stomach in order to prioritise more immediate and important ones (hence also why we associate 'cold feet' with anxiety: stress literally does have that effect).

The problem is that stress, despite being an evolutionary response to predominantly physical danger, is the only real response we have. It is a kind of one-size-fits-all solution. Therefore, when we experience stress of different kinds - namely emotional stress, in the form of work problems, relationship issues, money worries and other types of challenge - the stress response is applied anyway. Thus we find that our body physically prepares for a situation that may be far removed from the one we are actually in.

This is the root of stress-related illness. Stress evolved as a quick-fix response: its job is to get you out of trouble now by avoiding an immediate and physical threat. Where that threat cannot be solved - such as in the case of a troubled relationship, which requires a more complex solution - the physiological response is maintained. This means that the effects of stress can be felt for the long term, rather than the brief period of time that, in evolutionary terms, it was required. (This, incidentally, is one reason that exercise is great for relieving stress - it's one way of using that energy physically, in the way that was intended.)

In practice, this means that it's worth examining the implicit assumptions you make about the stressful situations you find yourself in, and whether they warrant the response they provoke - the chances are not. Sometimes, exercise or a relaxation technique might be enough to help. On other occasions, adjusting your emotional response might be helpful, through questioning the reasons you feel the way you do.

Guy Brandon is a counsellor, author and founder of www.StressingOut.org, a website dedicated to stress, depression, anxiety and related issues.

For more about stress, see http://www.StressingOut.org/what-is-stress/.