Anxiety is usually triggered by an event or perception of how a future event may play out.
This could be public speaking or important meetings as examples but may even be seemingly insignificant events to others. Money and work related issues as well as family discord are the most common contributors. Agitation and a nervous disposition are often the key indicators externally.
It is a stress reaction that in small amounts is normal as part of the flight/fight response, but in excessive amounts can cause excessive sweating, dry mouth, irritability and muscle tension such as grinding of teeth or a sore jaw, it can proceed to a panic disorder, risk of cardiac problems and upset tension or insomnia.
When anxiety is extreme and prolonged in time, you can experience General Anxiety Disorder (GAD), the symptoms of which can be reduced with your therapeutic journey.
Another very common form of anxiety is Social Anxiety, which preclude the possibility to be with others or often in new situations involving people. This can be very debilitating, as you can reach a point where you avoid any social situation and withdraw from possible friendships. In extreme cases, people become bounded in their own home, not able to leave their known house and environment (in case of Agoraphobia).
Anxiety can be reduced by sharing problems with others who may help to re-frame situations with less severe results than anticipated but there is a tendency to self-medicating, using alcohol or drugs to lessen the short-term impact of the symptoms or numb the agitation. The likely longer-term results of the latter two will often result in an increasing of the problems and therefore the symptoms. Longer term anxiety will often lead to depression or anger or just an irritable disposition.
Anxiety is often treated in a psychological environment and may be complimented medicinally. Often the psychology will involve identifying stressors and employing mitigating strategies, ideally to prevent magnification of problems, removing the negative responses or pessimism and sometimes employing relaxations strategies and techniques.