Patrick Dempsey "was a serial monogamist"

"I've never found it easy to have one-night stands ... it tears away at your soul," the Grey's Anatomy and Made of Honor star, 42, tells the U.K. edition of Glamour" magazine for June. "By the time you open yourself up, you have to close yourself off."

Dempsey credits his spouse, with turning around his life after years of losing out on roles, partly because his dyslexia made it difficult to learn lines for auditions.

"Our relationship is stronger than ever because we know the difference between what is fantasy and what is real. We are in our 40s, not our 20s. We're not caught up in that whole McDreamy thing."

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