We can characterize anxiety as an excess amount of energetic intensity that can either overload or energize your ability to function and focus. When you can take that energy and find a creative and positive way to funnel that energy toward a successful outcome, you are optimizing that energy.
On the other hand, when that energetic intensity begins to make you feel or act incompetently or negatively or not at all, then anxiety feelings results.
For instance, if you are driving your car--calmly and normally and suddenly you need to respond to an emergency situation, your anxiety in the moment can flash you into handling the car competently and swiftly toward the safest outcome possible.
If you begin to experience flashbacks - vivid memories & experiences- of that incident and then experience anxiety, you are responding not to the need of the moment but to the traumatic effect of your past.
Traumatic events, as you can tell, can cause you to be stuck in past anxious events. When you are stuck in those events, and impaired by the emotional reliving of those events, you likely have what is called a Post Traumatic Stress Disorder.
Post Traumatic Stress Disorders are common among soldiers, abused children and adults, survivors of natural disasters, witnesses or victims to war time activities, witnesses or victims to crimes, etc.
Obviously, these are very intense events. Most of these events are chronic over extended amounts of time and thus the traumatic events are multiple, sudden, unpredictable but recurrent and very life threatening. No one would emotionally wish to be exposed to these horrific sites or first hand threats.