"You can never take your marriage for granted," he told People magazine.
"It goes to the idea of where you spend your energy and attention: Do you spend it with strangers, trying to show everybody how nice you are? Or do you cherish your partner and really don't worry about other people?"
"Like a lovely orchid, or anything else that's nurtured, marriage prospers and grows, but if it's ignored, it withers," Douglas said.
"You also have to be careful because kids are all-consuming. Kids have no sense of boundaries yet. You can exhaust yourself with the energy you put into your children so there's none left for the two of you. It's a dangerous seduction you fall into, with the best intentions. You have to watch that one."
The son of Hollywood legend Kirk Douglas, the two-time Oscar winner advises on being honest with your children, even through the rough times.
"I'm more and more prone to tell kids just about everything. There's been a while school of thought about things you should not tell children — if there's a problem in a relationship, people say, 'Let's not let the kids know,'" he said.
"Kids know. They know everything. I would err on the side of pretty much sharing everything. They can digest it, you know? It's life."
In 2011 Zeta-Jones checked into a mental health center for treatment of her bipolar disorder, because of stress perpetuated by Douglas' brave battle with throat cancer.
Although absent from the ceremony, Douglas thanked his wife in January while accepting the Golden Globe Award for Best Actor in a Television Mini Series for his portrayal of Liberace in Behind the Candelabra.