What is the difference between regular anxiety and an anxiety disorder?

At some time, most of us feel afraid, tense, or even anxious enough to become short of breath. The difference is that people who don't have anxiety disorders experience these reactions in response to genuine threats. When a fire is raging in the house next door, for example, anxiety can be a lifesaver, spurring an individual to flee the area near the burning building. But people with anxiety disorders face worry and fear in ordinary, relatively harmless situations. While tapping the keyboard of a computer, let's say, they may fear contracting a life-threatening disease (a sign of obsessive-compulsive disorder). They may be gripped by worry nearly every day about getting into a car accident, losing their job, having their children do poorly in school, or other possible but unlikely prospects (a sign of generalized anxiety disorder). People with anxiety disorders are hypersensitive to the possibility of danger. Yet their extreme vigilance serves no purpose. They are spinning their neurobiological wheels, so to speak.