Stress management is the art and science of minimizing the harmful effects of stress and maximizing their beneficial effects.  Since stress is part of everyone's life, it needs to be managed like any other aspect of life.  Stress management, to some degree, is a question of not allowing stress to change one's healthy habits.  For example, a person under stress might eat poorly, sleep less, and feel unable to exercise.  Doing any or all of those will does not promote wellness at all.  For example, not sleeping 7 1/2 hours nightly can affect one's insulin production and lead to diabetes and also affect one's proper brain functioning.  There is some evidence that stress can weaken our immune systems.  And certainly, not exercising or eating properly is bad for us in innumerable ways.   This is why people speak of managing stress, so it doesn't manage them and result in physical and mental consequences that are not good.  Stress can, of course, be good for us, in that it can send hormones through our bodies and brains that help us to the things we need to do and that help save us if we are in danger.  However, some people seem to become a little addicted to that feeling, and their stress is managing them, giving them more of those hormones than they need, and harming their bodies and their brains.  Since stress is a part of life, its management is a necessity for physical and mental well-being.