While fear triggers the full response system at the moment of danger, anxiety triggers parts of the same system when a threat is merely perceived as possible. It is healthy to be anxious and on alert when one is in a situation where there really could be dangers lurking. But when our alarm bell is on a hair trigger so that it is frequently activated by ordinary events—including many that pose no real threat—it keeps us in a perpetual state of distress. This is when ordinary, healthy, temporary anxiety turns into an anxiety disorder.