Anxiety is an emotion which I am sure we all have experienced more times than we would have liked to. Some of its common symptoms are sweaty palms, an increase of the heart rate and more blood flowing through the vessels, besides it is caused as a response of a real or imaginary threat.
This feeling has been a true savior during evolution. "Fight or flight" is a reaction that has kept us alive, surviving dangers of predators and other dangerous situations that could have resulted in death. Furthermore, anxiety has another positive aspect applicable in nowadays' lifestyle and it's that anxiety pushes us to improve and do our best. If we didn't have this natural response we wouldn't be able to study hours and hours to do a good exam or to keep awake finishing some project. Quoting a CEO "Anxiety and a brilliant brain is the key of success".
However, anxiety is not a motivation to do things for everybody , some people find this feeling overwhelming and it disables them to do the pending tasks. Also for some people even a small decision triggers anxiety. In these cases anxiety is considered an illness and should be assisted.
Furthermore, we might be anxious for a long period of time, for instance we might be anxious due to an exam for days or even weeks, and that is not healthy at all.
To put it in a nutshell, anxiety is a natural feeling that we should be able to handle. I believe that most of it comes from school/work related matters ,so if we learn when it is worthy to worry and when it is not we will drastically reduce our likelihood to feel anxious.