Our lives are full of demands at all different levels. All demands effect us. Some to a mild degree and some not so mild. Well, it stays on. As a result, you might start to experience general symptoms such as anxiety, depression, negative mood states including anger or irritability, or stomach cramps and headaches.
Relaxation is the process of turning-off the response to demand.
Most relaxation exercises involve slowing down your breathing. This then changes the chemistry of your body and has a flow-on effect that generally calms the nervous system. The problem with the 'breathing-down' style of relaxation is that it irritates some people. Some people find it difficult to concentrate. Other people are very sensitive to increases of CO2 in their blood and get panicky.