The 69-year-old actor and 44-year-old actress have been married for over thirteen years, but temporarily split for a six-month period in 2013. The marriage was reportedly put under strain by Douglas' tongue cancer diagnosis and Zeta-Jones' stay in rehab.
The couple are now reconciled, and Douglas tells The Sun the rocky patch made him appreciate his wife and their two children.
"First you have to admit that you made a mistake," the actor relates. "Then dealing with it is easy. Of course it's important to make mistakes, as long as you grow from them."
"When you are younger, you care what other people think and you take the person closest to you for granted," he continues. "You waste a lot of energy on strangers to make a good impression. When you're older you focus that energy on the people closest to you, on your family and you're courteous."
Douglas will next appear alongside Diane Keaton in And So It Goes on July 18, while Zeta-Jones is rumored to star in the upcoming movie Vivaldi.