In the literal sense, stress means a pressure or force that is exerted against something. In human terms, it is the way that we respond to pressures or demands that are being made of us. Stress is a normal part of being alive. It is impossible to live a completely stress-free existence, and you wouldn't want to. Stress adds excitement to many of the things we do.
Stress also plays an important role in human motivation.
During competitive sport, the stress of competing motivates you to play well, just as the stress of a reasonably demanding job keeps you on your toes, performing well. Experiencing a reasonable degree of stress is not a problem - the important factor is feeling in control of the situation. Each of us has our own unique set of stressors and ways of responding to them. This will involve writing down some specific goals. Be prepared to do whatever is necessary to find them.