Han Sun

“One noteworthy study suggests that people who suppress negative emotions tend to leak those emotions later in unexpected ways. The psychologist Judith Grob asked people to hide their emotions when she showed them disgusting images. She even had them hold pens in their mouths to prevent them from frowning. She found that this group reported feeling less disgusted by the pictures than did those who'd been allowed to react naturally. Later, however, the people who hid their emotions suffered side effects. Their memory was impaired, and the negative emotions they'd suppressed seemed to color their outlook. When Grob had them fill in the missing letter to the word "gr_ss", for example, they were more likely than others to offer "gross" rather than "grass". "People who tend to [suppress their negative emotions] regularly," concludes Grob, "might start to see their world in a more negative light." p. 223”
― Susan Cain, Quiet: The Power of Introverts in a World That Can't Stop Talking