Harry Hamlin Shares What He's Learned About Marriage After 25 Years with Lisa Rinna: 'We're Not Clingy'

Harry Hamlin knows a thing or two about maintaining a healthy marriage.

In this week's issue of PEOPLE, the actor, 71, opens up about his 25-year marriage to Real Housewives of Beverly Hills star Lisa Rinna, the secret to their lasting relationship and the lessons he learned from his previous marriages.

"I'm different from a lot of men in my generation because I did not play the field," says Hamlin, who was previously married to Laura Johnson and Nicollette Sheridan before marrying Rinna in 1997. "The number of people with whom I've been intimate is not very many — I marry them, mostly. Probably the first couple [of marriages] were me trying to work stuff out because they had characteristics that were similar to my mother."

"Having a degree in psychology allows me to go back and research from this book, which is very helpful when you're trying to figure out who the f--- you are," Hamlin says, as he pulls Diagnostic and Statistical Manual of Mental Disorders from his bookshelf.

"I think a lot of people end up trying to work s--- out with their lovers," he adds. "Breaking the cycle is not easy. Having not married my mother the third time, then comes the challenge: How do you make that friendship and relationship work both romantically and platonically?"

Hamlin ultimately figured out how to make things work with Rinna, 59, with whom he shares daughters Delilah, 24, and Amelia, 21. Last March, they marked 25 years of marriage.

"'Happy wife, happy life' really is my mantra," Hamlin says. "And it works. We listen to each other, and we're not clingy. She does what she wants, so I can do what I want."

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Hamlin — who is also dad to 42-year-old son Dimitri with former girlfriend Ursula Andress — has previously spoke about his successful marriage, telling PEOPLE in February: "[The secret is] being diametrically opposite."

"I like going up to the mountains, and her idea of camping is anything below the 10th floor of the Four Seasons," he explained.

Hamlin and Rinna also admitted at the time that their road to happiness had its early bumps.

"She played hard to get," the actor said of his first attempts to court Rinna. "The Rules (a trendy self-help guide to dating) had just come out and it was written by women, for women to teach them how to get a man. And in that book, one of the rules was, if you were called up by somebody and they asked you on a date, you had to say, 'No.' You had to wait at least a week or whatever. And I knew that she had read that book."

Hamlin added, "So I called her up and I said, 'Do you want to come to dinner at this Italian restaurant?' and she said, 'When?' I said, 'Well, how about in an hour?' And I hadn't talked to her in months. And, she showed up and broke all the rules."

"I'd just come from work [on The Days of Our Lives] and had no makeup on," recalled Rinna. "So I guess I wasn't playing that hard to get."

RELATED VIDEO: Harry Hamlin on the Secret to 25 Years of Happiness with Lisa Rinna: 'We're Diametrically Opposite!'

Besides prioritizing his marriage, Hamlin has been focused on two big projects coming in the next month: his AMC series Anne Rice's Mayfair Witches (premiering Jan. 8) as well as the film 80 for Brady (opening Feb. 3).

Along the twists and turns of his five-decade career, Hamlin tells PEOPLE in this week's issue that "acceptance" has become one of his biggest life lessons.

"The idea of acceptance and allowing the universe to be what it's going to be, and accept that it is what it is. Otherwise, you'll spend your life trying to smash a square peg into a round hole," he shares. "I spent many years doing that so I decided to toss my hammer away and just accept things."

For more on Harry Hamlin, pick up the latest issue of PEOPLE, on newsstands Friday, or subscribe here.