"I call it a congenital sadness. It's something I feel in my grandparents, in the people I've met, in a southern way of life. It's something pervasive, an undercurrent," The Sun quoted him, as saying.
However, he also admits that having his family - partner Angelina Jolie and kids Maddox, Pax, Zahara and Shiloh - around him works as a charm to keep this sadness at bay.
In an interview with the Mirror, the actor had revealed that his kids constantly make him smile.
"The kids are fantastic and they sometimes get unruly and say the funniest things I've ever heard. Man, they're the funniest people I've ever met," he said.
"It's strange the chaos they cause. We move into a hotel room and boom! It's external chaos but it's the eye of the storm, too, because it's actually very calm. It's calming to me," he added.