To have moments in your life when you feel anxious is normal. A first date, first day on a new job...are normal feelings of anxiousness because it's something new and exciting. The unknown can cause us to feel a little anxious sometimes but eventually we get over it.
Then there are times for some people when it's not that easy. Anxiety rules life. Fear becomes your best friend. Even things you have done before will now make you feel anxious.
You may even avoid social gatherings. Large crowds become overwhelming to the senses. High levels of anxiety can cause us to shut down and close out the world.