The comfort zone
is, as might be expected, the zone
in which one is comfort
able. It encompasses everything you are willing to do or experience.
For example, mine allows me to eat almost any food, no matter how spicy; when people whose comfort zone does not encompass said food witness this, they often become displeased.
This brings us to the next point - leaving the comfort zone is extremely uncomfortable, but is necessary in order to stay sane and not be trapped, unable to act, in one's own body, as are many mental patients.
When the comfort zone is excedded habitually and stretches too far, on the other hand, one is liable to become a daredevil and cause physical or psychological harm to oneself by doing stupid things that a more rational person would not.
Inspired by a section of the best-selling book Life 101 read several years earlier