Anxiety and fear are normal human emotions that can help us deal with danger. But some people experience excessive and irrational, irrational anxiety which is indicative of an anxiety disorder. Symptoms like panic or anxiety attacks or fear of these attacks in inappropriate situations really intense physical reactions. Avoidance behavior is actually one of the key pillars of anxiety disorders. A person who's suffering from something like a social phobia may go to extreme lengths to avoid a situation that they think could bring on anxious feelings.