“Get married properly! “A Bad Marriage Ages You” (Exclusive)

The 'Rebel Ridge' and 'Doctor Odyssey' star shares his secret to looking and feeling young at 74

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Four decades after his iconic series MiamiVice debuted, Don Johnson still has one moment.

The 74-year-old actor is currently starring in two back-to-back projects: the hit Netflix film Rebel Ridgeand Hulu's new series Doctor Odyssey. He looks fitter than ever. His secret?

“Get married properly!” he tells PEOPLE with a laugh. “A bad marriage ages you.”

Of course, the father of six, who has been married to Kelley Phleger since 1999, says the only other way to look and feel young is to simply keep moving.

Related: Don Johnson on 'Keys' to 25-Year Marriage to Kelley Phleger: 'Unspoken Trust and Kindness' (Exclusive)

“You have to exercise, and exercise a lot,” he says. “How do you think I had six children?” He jokes: “At least I know that!”

Johnson had those celebrity looks, but also became a (reluctant) fashion star for a while in the '80s with the pastel linen suit and loafers with no socks that he wore MiamiVice suddenly became the de facto wardrobe for hot guys around the world.

Gary Null/NBCU Photo Bank/NBCUniversal via Getty

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In a 1985 PEOPLE cover story, he revealed that he didn't love all of Detective James “Sonny” Crockett's carbon copies.

“It's the only look I've ever liked and felt individual in, and now every man, his brother and his dog are wearing it,” he said. (He also revealed his secret to keeping stubble lasting for two days: “I shave with a sideburn trimmer.”)

These days, Johnson doesn't care about clothes or stubble—he's just glad it's “still on the menu.”

“My goal back then was not to be Sonny Crockett forever,” he says of trying to cope with the hit show's popularity. “I had seen the danger posed by actors who identify too much with their characters. I felt like I had to separate myself from Sonny so that people could eventually see me as other characters.”

Related: Don Johnson Says Being an '80s Heartthrob Was Dangerous: 'We Had to Have 24/7 Security' (Exclusive)

Of course, he has experienced many ups and downs over the past few decades MiamiVice ended in 1989 after five seasons.

“I had breaks in my career where I wasn’t sure if I would ever get a job again,” he says.

“I've always said that as an actor you go through these phases: 'Who is Don Johnson?' Then: “Get me a Don Johnson!” Then: “Get me a Don Johnson.” type!' Then: “Get me one younger Don Johnson!' And finally it's back to 'Who is Don Johnson?'.”

He shrugs his shoulders and laughs. “That’s just the way it is.”

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Read the original article on People.