Anxiety is a very natural thing, felt by all human beings. Anyone can experience it, and, like stress, it initiates a response that is commonly known as the fight or flight response. When you imagine that you are in danger or you imagine something dangerous could happen, the fight or flight response is activated. Anxiety is often a response to an imprecise or unknown threat.
Although most people experience a relatively mild form of anxiety when facing particularly stressful situations (such as public speaking or presentations), anxiety can be so severe that it disrupts you going about your daily life in a calm, controlled way. Often, people choose to avoid situations that may raise their stress levels and cause the flight or flight response, but this can lead to not achieving your full potential or being unable to develop deeper personal relationships. Anxiety can manifest as panic attacks, constant worry, muscle tension, or butterflies in the stomach.