Psychotherapist and social worker Amy Morin detailed the key characteristics mentally tough people have in her bestseller, "13 Things Mentally Strong People Don't Do."

Mentally tough people refuse to give up after failure and don't let others' judgments affect them.

Like physical health, mental toughness must be worked on, Morin said in her book.

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Mental strength isn't often reflected in what you do. It's usually seen in what you don't do.

In her bestseller "13 Things Mentally Strong People Don't Do," psychotherapist and social worker Amy Morin wrote that developing mental strength requires a "three-pronged approach." It's about controlling your thoughts, behaviors, and emotions.

Like physical health, mental toughness must be worked toward, Morin said. Knowing how to regulate your thoughts and control your emotions helps build mental toughness.

The following are 13 things that mentally strong people do not do, according to Morin.

This is an update of an article originally written by Steven Benna.