Patrick Molloy has a great fear of offending people. At the end of each day, he replays every one of his conversations and interactions in his head, to figure out if he needs to apologize to anyone.

The 44-year-old graphic designer says it’s nearly impossible to turn these swirling thoughts off. “It feels like an unwelcome guest in my mind,” says Mr. Molloy, who lives in West Sussex in the U.K. “It’s wearying and it’s discouraging.”

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