Maybe he shouldn't have left his wife...
Consider this: He was married to Cindy Silva for 16 years, from 1978 to 1994. The height of Costner's career ran parallel to these years. From 1987 to 1993 he was hot stuff. Untouchables, Bull Durham, Field of Dreams, Dances With Wolves, JFK, The Bodyguard, Perfect World.
Then in 1994 he divorces Cindy. Not one year later he stars in the mediocre, dissapointing blockbuster Waterworld. After that, it was only a couple of years until he permanently sabotaged his own career with the box office bomb The Postman, from which he has never really recovered.
My hypothesis is that maybe he should have stayed married to Cindy.
~ I'm a 21st century man and I don't wanna be here.