Science Proves What Doesn't Kill You Makes You Stronger

To a degree, yes.

Tough experiences do seem to make you tougher. People who had faced a moderate amount of adversity often coped better with problems than those who had a history of either serious problems or none at all:

Via APS:

Your parents were right: Hard experiences may indeed make you tough. Psychological scientists have found that, while going through many experiences like assault, hurricanes, and bereavement can be psychologically damaging, small amounts of trauma may help people develop resilience.

And:

Indeed, a lot of solid psychology research shows that having miserable life experiences is bad for you. Serious events, like the death of a child or parent, a natural disaster, being physically attacked, experiencing sexual abuse, or being forcibly separated from your family, can cause psychological problems. In fact, some research has suggested that the best way to go through life is having nothing ever happen to you. But not only is that unrealistic, it’s not necessarily healthy, Seery says.

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