When we consider the effects of stress on our well being, it makes a lot of sense to spend some time understanding our personal stress triggers, how they came out and what we can do about them.
While it is tempting to consider an external stress trigger as the cause of stress, a little more consideration will reveal that the same situation like public speaking, an interview, negotiating with your boss, a MRI scan etc. will draw out widely different reactions from different people.
The stress response is driven by the individual perception of a threat. But if the perception of threat is inaccurate, there is a cost to pay in terms of life or well-being.
If you correctly perceive a lion chasing you as a threat, your body will marshal energy to run faster to safety and give you a better chance at surviving. If the chasing lion is not considered a threat, there is a good chance of death.
If you incorrectly perceive an interview as a threat, the same reactions that can save your life will dumb down your thinking process and lead to panic/dump reactions and consequent failure. Not having the threat response in this situation will result in a better performance.
Perception as I have been using the term is a mix of external sensory stimuli that correspond to an external event or situation and an individual's internal response to it.
The internal response is generally automatic and it constitutes our emotional reactions like fear, anger, anxiety, etc. It is usually accompanied by specific individualized body sensations like tightness in the chest, weakness of knees, pain in the neck, heat in the face etc.
If we wish to avoid the harmful effects of stress in a particular situation like an interview or a negotiation or a talk, the only way out is to change our internal response to that situation.
There are many practical theories proposed to explain our internal responses and methods to alter them.