Anxiety is a problem more common than you might think. Everyone experiences anxiety to some degree. It is nature's alarm system to signal fight or flight in times of danger, adaptive if you see a bear in the woods. However most situations don't literally require fight or flight. They require social or mental performance.
Some anxiety is positive.
Social psychology research has shown that moderate levels of anxiety enhance performance for a familiar or well rehearsed task. However, many people suffer from debilitating anxiety disorders of different types. Anxiety is one of the most frequently reported health problems. There are many types of anxiety ranging from common phobias to more severe and persistent anxiety disorders that can cripple your ability to engage in routine activities. Many factors may lead to the development of anxiety disorders including faulty learning, a nervous system that is more reactive to stress, physical illness, or excessive levels of stress.