Anxiety disorders come in many shapes and forms. People with panic disorder have chronic, unexpected, and repeated panic attacks where they feel an overwhelming sense of being in danger. Sufferers of generalized anxiety disorder have persistent and exaggerated worries and constantly expect disaster. Those with obsessive-compulsive disorder have unreasonable fears that they try to deal with through repetitive, ritualized activities such as hand washing. A phobia is an irrational and uncontrollable fear of a specific thing, while post-traumatic stress disorder occurs after a terrifying event and causes its victims to have flashbacks or frightening thoughts of the incident.