Even Keith Richards knows that heroin is a beast. From what I'm reading, he seems to be saying that he can still fuck with other drugs, just not heroin. I guess he's lived to be 63, muttering and mumbling and being utterly fucking incomprehensible.
He's another example of someone filling me with hope and despair at the same time. I see him and think, "He's a terrible addict, and he's lived to old age. Maybe my husband can, too." And then I think, "Do I want to live with a muttering old addicty fart until he's 63?"