Anxiety

Anxiety, within limits, is a part of normal life, but excessive anxiety is an illness by itself, as well a part of other psychiatric illnesses.

Normal anxiety is a natural phenomenon and helps people to attain their goals e.g. if someone is anxious about failing in examination, he will work harder and thus anxiety increases the level of performance. Anxiety will be considered an illness when it becomes so severe that it decreases the level of performance instead of increasing it.