Researchers have found that the highest rises in cortisol levels — the most extreme fight or flight response — are prompted by "threats to one's social self, or threat to one's social acceptance, esteem, and status."
Just think about the difference between hearing a compliment and a criticism. Which are you more inclined to believe? What do you dwell on longer?
The researcher John Gottman has found that among married couples, it takes at least five positive comments to offset one negative one.