Clint Black and Lisa Hartman Black's one rule that has kept their marriage strong for nearly 35 years

For Lisa Hartman Black and Clint Black, nearly 35 years of marriage started with one simple promise: When they said "I do," they meant it.

The "Knots Landing" alum and country music star are teaming up for a new Lifetime movie, "When I Said I Do," inspired by their 1999 duet. The movie tells the story of Ali Corley (Sarah Drew), a widowed search-and-rescue K-9 handler who rebuilds her life and finds love again after losing her husband in the line of duty.

The couple, executive producers of the movie, also make special appearances as themselves, hosting a relationship podcast.

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"Years ago, Clint wrote this song and asked me to sing it with him, and I was afraid to do that," the actress told Fox News Digital. "I gave in, fortunately. And here we are today. We’ve had so much success with it — from chart success and awards to nominations, people getting married to it and couples renewing their vows [to it]. We just feel honored to be a part of it."

The country music power couple met backstage after one of Black’s concerts on New Year’s Eve 1990. They married Oct. 20, 1991, and welcomed daughter Lily Pearl Black in 2001. Their romance has spanned more than three decades.

"We strongly believe in communicating," the 69-year-old said about the one secret to their marriage. "It sounds so simple, but you really, really have to talk everything through. Roy Rogers said to Clint, ‘One piece of advice: Never go to bed angry.’ And it’s true. You can’t get in the car and drive away. You’ve got to talk it out if you can. A lot of times, you find it was just misinterpreted."

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"Communication is important," she stressed. "Misinterpretation, unfortunately, is part of the deal. [But] you can clear the air and [say], ‘Oh, that’s what you meant!’ And you know your partner’s heart. I know, and he knows, that we would never mean to hurt each other. He would never intentionally hurt me. But sometimes feelings get hurt. If you can explain yourself, it makes all the difference."

"Really, it’s communication," Hartman Black insisted. "And he’s my friend. He’s my best friend. When you treat each other that way, you have to honor your friendship, trust it and respect it. We’ve somehow managed to do that, and here we are nearly 35 years later."

The couple has endured personal heartbreak. In his upcoming memoir, "Killin’ Time: My Life and Music," Black wrote that he and his wife experienced four pregnancy losses before welcoming their only child, People magazine reported. According to the outlet, they kept the losses private to "keep hope alive." The 64-year-old wrote that they "got through it together."

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"In the early years, we basically knew we wanted to have children," Hartman Black said. "But the [running] joke was, we have dogs, we can put them in the backyard, and we can go to the movies, and we won’t go to prison. That's Clint's joke.

"[But] when we decided to have a child, it was, ‘No, we’ve got to do this now.’ It couldn’t happen fast enough. And it was amazing how we both just went, ‘baby time.’"

"When she was born, he took off the first three years," Hartman Black recalled. "We were just parents during those first three years. Not everyone can do that, but it worked for us. Looking back, I’m so glad he was there. It was a special time."

Hartman Black said that her husband still gives her reasons every day to fall in love with him all over again.

"People have asked me about his legacy, what I want people to remember him by," she said. "He’s a good, solid man. What you see is what you get. … And it goes back to how we communicate. You don’t fight, you don’t yell. … We get along. And I think that’s underneath it all. And we laugh so much — sometimes through tears. And that is a very special thing to have with your partner. We’re just there for each other. We feel very blessed, very lucky that we found each other."

"And our daughter — we’re this great little trio," she gushed. "I thank God every day. She just turned 25. She’s got her dad’s writing gene. She’s got a phenomenal voice. I wanted her to be a veterinarian. … But no, she’s incredibly talented."

"It’s so much fun for the three of us to be together, whether it’s having dinner, watching a movie or reluctantly taking him shopping. It’s the simple little things, but we know how lucky we are. We’re lucky we made it here. We’re lucky because it was hard to get there, and we’re all best friends. It’s a beautiful thing."

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Remembering how she met her husband, Hartman Black said it felt like a movie — as if time slowed to a crawl and every sound around her faded into a soft, distorted blur. Nearly a year after their first dinner together, they tied the knot.

"We met when we were older, established in our careers and had lived some life," she explained. "… We had been on the fast track, and I think that grows you up sometimes. I think we were mature enough and knew what we wanted, knew what was important [when it came to] values and morals — things like that. We were totally in sync. I think that’s what fast-tracked us."

"We were just so in sync and had great conversations," she said. "He’s one of the funniest people you’ll ever meet. And I’m funny too, but not like him. He’s just amazing."

While juggling fame and family, the couple remained devoted to each other and always gave one another space to share their feelings.

"I think after all these years, there are still many things we do for each other," Hartman Black said. "I think that’s why we’ve endured and why we’re still together. Again, it’s communication. Talk it through.

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"I know when to just listen, and he does the same for me because we’re both pretty driven and high-energy. He’s laid back in his way, but he’s got a strong work ethic and a lot of drive. I think it’s easier for me now to step back and let him vent or do whatever he needs to do."

"With us, we always talk about things," she said. "After all this time, you know each other inside and out. You pay attention to each other. You respect each other. You’re really in tune."