Your body has a natural response to threats. If something dangerous is happening, our bodies will produce a reaction to let us know that we need to run away - this has been labelled the "stress response", or the "fight or flight" reaction in the past, and today is also frequently referred to as "pressure". In the context of imminent danger, this acts as a protection mechanism and is not a bad thing.
A small amount of pressure is also not a bad thing in everyday life. We all need that feeling of urgency that helps us get out of bed each morning to go to work, or the slight feeling of alarm which helps us to cross the road quickly when we see a car coming. However, too much pressure can lead to stress, which serves no useful purpose whatsoever, and can cause physical and emotional harm. Far from helping us to function better and keeping us safe, stress can make us more inefficient, by stopping us from sleeping, making us feel overly tense all the time, along with a host of other adverse effects.
Stress is a medical condition and it can have a serious effect on your health. If you think you are suffering from stress it is crucial that you consult a medical professional.