Difference Between Worrying, Anxiety, and Stress
In short, worrying is a thought, anxiety is a feeling, and stress is a physical reaction.
Worrying is a thought. It comes from the thinking part of the brain which is the cortex.
Worrying is repeative troubled thinking usually about the future or past. It is opposite of "be here now". It is not of the present moment. Worrying is mostly thought, mainly imaginative thoughts of worst senarios circumstance.
However, most things that we worry about never happens. So in a sense we have wasted our energy for nothing. If we know most of our worry thoughts don't happen, then perhaps we can to some extent stop our worrying.
Anxiety is a feeling. It comes from the emotional limbic system of the brain.
It may be accompanied with physical symptoms like sweaty palms, shortness of breath, rapid breathing, tightness of chest. Feeling of something bad about to occur.
Anxiety in the extreme is a panic attack. A panic attack is a feeling of impending doom or the feeling that one is about to die.
Stress is a physical response to a real or perceived threat. In the prehistoric days, it would probably be due to a physical threat like a tiger. But in the modern world, it would probably be due to a virtual or imagined threat -- like stock market plunges, bad news, possibility of losing our jobs, etc.
In the pre-historic days, the stress chemicals is dissapated by physical action of running away from the tiger. And then there is no more stress. That is why zebra doesn't get ulcers. But in the modern days, we have chronic stress which is harder for us to dissapate. That is why phyiscal exercise can help relieve stress.
Because stress can be due to perceived threat, what is stressful to one person may not be stressful to another. That is why one person may perceive a threat in a particular situation; whereas another person may not perceive such a threat in the same situation.