I don't know what demons he wrestled with, but it's sad to hear that he didn't want to fight them anymore.
I acted with David Carradine in the second of his Kung Fu TV series. I played the rather "flamboyant" owner of a drag queen night club where Carradine and his cop son go undercover. My big scene was when I proposed that Carradine's son, (played by Chris Potter) wear a wedding dress since at my club, "the waiters are women, Mr. Caine." It was a rather snappy scene requiring a bit of comic timing.
Unfortunately, when we shot the scene, (the first of the day), Carradine was too drunk to act. So the director shot around the missing star and we acted with Carradine's stand-in stiffly reading his lines. Finally, Carradine was needed for his dialogue and he got through a take or two before it wasn't really worth continuing. By the end of the day, Carradine was yelling at the extras. So it wasn't the greatest acting experience for me, however, the scene was on my acting demo reel for years--mostly because of the role I played.
I dined out on my tale of working with David Carradine until recent years when the word was he'd dried out and turned over a new leaf, earning the titular role in Tarantino's two-part film, Kill Bill.
So I'm sad to hear of his self-imposed passing. David Carradine had talent--his portrayal of Woody Guthrie is quite remarkable--and he had opportunities that most of us can never dream of, like becoming the iconic Kwang Chai Caine. I'm glad I had a chance to work with him and perhaps learned from him how not to deal with fame. I hope he is finally at peace.