Oliver Hudson Reveals the Relationship Rule He and Wife Erinn Have After 18 Years of Marriage (Exclusive)

Oliver Hudson and wife Erinn Hudson know how to keep their marriage strong.

While attending an event held by the Goldie Hawn Foundation to celebrate the 20th anniversary of the MindUP Gala in Los Angeles on Sept. 27, the actor, 48, opened up about the relationship rule he and Erinn, 51, have after 18 years of marriage.

"You never want to go [away from each other for] too long, but if you're in this business, you're going to be away," Oliver said. "I always make it a point to come home anytime that I can."

"But aside from that, I think it's just more about individuation," he continued. "I think there's a tendency to become codependent, where it's like, when you're feeling bad, I'm feeling bad. We are a unit, yes we are, but we are individuals. You need to go do your s- and let me go do my s- and be okay with it."

"If I want to go play golf, if I want to go fish, let me do that. If you want to go be with your girls, if you want to do whatever you want to do, you can do that," added The Cleaning Lady star. "I think that that's the most important thing."

Further detailing his strong relationship with Erinn, Oliver compared their marriage to "holding up a slab of marble."

"If you have one pillar, that s- will teeter and probably fall. If you have two, there's more stability there," he explained to PEOPLE.

Oliver added, "So if we got two of them, that structure's going to stay intact, and that's how we navigate our stuff. You know what I mean?"

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Oliver met Erinn in Sandy Marshall's acting class in the late '90s. Though Oliver had a girlfriend at the time, he and Erinn became friends, and after about a year and a half, they took things a step forward.