Very true; the best guitarist I've ever known was a (mostly) functioning smack addict and he ruined every opportunity he ever had, burned through a fabulous collection of vintage guitars and ended up living in his parents' shed at the age of 40 due to his addiction. He finally went clean in about 2000, I'm glad to say, and has had a much better time of it since then. Where his talent could have taken him I don't know, but I do know exactly where heroin took him.