Goldie Hawn, 78, says the secret to her 40-year relationship is 'good sex'

• Goldie Hawn, 78, credits good sex as the secret to her long relationship with Kurt Russell.
• The couple first met in 1966 and have been together for over 40 years.

Goldie Hawn and Kurt Russell have been together for over 40 years despite not being married. And the secret to their long-lasting relationship?

"You have to have good sex," Hawn, 78, told E! News in a joint interview with Russell. "Because sex is something that connects you and creates more belonging. People who have healthy sexual relationships usually last a lot longer. But it's not just because of the act, it's because of the warmth and the intimacy that it creates."

The couple met for the first time in 1966 while on the set of a Disney movie. They reconnected in 1983 when they were cast in the romance drama "Swing Shift," and started dating shortly after. They welcomed one son, Wyatt Russell, together in 1986.

Their blended family also includes Boston Russell, whom Russell welcomed with ex-wife Season Hubley, and Oliver Hudson and Kate Hudson from Hawn's previous relationship with Bill Hudson.

Reflecting on the decades she spent with Russell, Hawn says it's normal for them to not always have the same perspective on things.

"You know you're not the same person," she said. "You don't think the same way oftentimes. And you have to accept that, but you have to measure are we having fun, or is this something we want to do? Do we have laughs together? Do we share certain things? You don't have to share everything."

In spite of the expectations one might have in a relationship, what matters most is that "you have to like the person," Hawn said.

Moreover, Russell added, that having shared experiences has helped strengthen their relationship.

"Most people that have been together for a long time, I think, share one thing in common, and that is that after that many years together, you will have experienced just about everything there is to experience together and understand all the ups and downs and what it means," Russell said.

The average adult has sex about once a week. However, sex therapists say that the quality of sex and the connection that one shares with their partner is more important than how often they have sex. Each couple determines the amount of sex that's right for them to have, and this may change over the course of the relationship, Stefani Goerlich, a licensed master social worker and sex therapist, told BI previously.

"I've worked with couples who would argue that once a week is too much, and others who would say it's not nearly enough," Goerlich said.

The benefits of sex go beyond relationships. It has been proven to reduce stress, improve self-confidence, and even boost immunity.

A representative for Hawn did not immediately respond to a request for comment from Business Insider, sent outside regular hours.