Think of anxiety as a network of neural clusters in the brain that create an area of association. For example, a piano player will have an area of association that correlates to the hands and feet used to play the instrument.
Neuroscientists like to say: "The cells that fire together, wire together." The more the pattern is reinforced, the thicker and stronger the cluster of neurons becomes, and as a result, it becomes much more difficult to control them and more easily triggered.
So every time you are anxious, you are reinforcing the pattern of anxiety.
So you have to break the pattern of anxiety to create new neural pathways.