"To both of us, it's like heaven on Earth," Danson tells PEOPLE of his morning routine with his wife of nearly 30 years

Just a year before meeting Steenburgen, Danson tells PEOPLE he had committed himself to being a better man: "I worked very hard at it or I don't think Mary Steenburgen would've even seen me"

Mary Steenburgen and Jack Nicholson costarred in 1978's 'Goin' South,' which marked Steenburgen's feature film debut