We generally use the word "stress" when we feel that everything seems to have become too much - we are overloaded and wonder whether we really can cope with the pressures placed upon us. Anything that poses a challenge or a threat to our well-being is a stress. Some stresses get you going and they are good for you - without any stress at all many say our lives would be boring and would probably feel pointless. However, when the stresses undermine both our mental and physical health they are bad.
Stress is related to both external and internal factors. External factors include the physical environment, including your job, your relationships with others, your home, and all the situations, challenges, difficulties, and expectations you're confronted with on a daily basis. Internal factors determine your body's ability to respond to, and deal with, the external stress-inducing factors. Internal factors which influence your ability to handle stress include your nutritional status, overall health and fitness levels, emotional well-being, and the amount of sleep and rest you get.
Most of us have varying interpretations of what stress is about and what matters. Some of us focus on what happens to us, such as breaking a bone or getting a promotion, while others think more about the event itself. What really matters are our thoughts about the situations in which we find ourselves.
We are continually sizing up situations that confront us in life. We assess each situation, deciding whether something is a threat, how we can deal with it and what resources we can use. If we conclude that the required resources needed to effectively deal with a situation are beyond what we have available, we say that that situation is stressful - and we react with a classical stress response. On the other hand, if we decide our available resources and skills are more than enough to deal with a situation, it is not seen as stressful to us.