Thoughts create anxiety. The human brain has the capacity for intelligent thought. The human brain also has the ability to distort reality. Quick, "snap judgements" can trigger anxiety before the intelligent part of the brain has a chance to evaluate carefully and accurately.

Thoughts that trigger anxiety may be preceeded by "WHAT IF...." and followed by a possible future negative event.

WHAT IF questions may focus on any topic. Here are two examples:

"What if I do not pass the test?"

"What if I do not get promoted?"

WHAT IF questions may trigger anxiety unless the intelligent part of the brain takes the time and trouble to respond with a coping solution.  

Breathing 

Exhaling fully is a key element in thinking. The intelligent part of the brain runs on oxygen. Unless you exhale, there is no room in your lungs for incoming oxygen.  

Quick "snap judgements" that trigger anxiety seem to trigger breath-holding. Within 60 to 90 seconds, the intelligent part of the brain does not have enough oxygen to produce intelligent thoughts.  

A vicious cycle then begins. "What if" thinking takes over without solution-focused, calming thinking, and shallow or panic breathing fails to oxygenate the blood flow to the brain.