He's like Fleetwood Mac's Syd Barrett. In his case, hanging out with these people and some heavy acid trips did it for him. R.I.P. Peter Green R.I.P. Danny Kirwan
No, it's probably just because you've gotten older and the ones you know/care about from your youth are starting to die off. All the musicians, actors, etc. from the 70's-90's have gotten old... Hell, the greatness that is Olivia de Havilland (Gone with the Wind among others). She was 104, so no thread.
