Reality bites -

John Lennon - took himself too damn seriously and got shot in the face by a man who was ironically reading The Catcher in the Rye. (Yeah, this is destiny's unstoppable irony - if the guy was coming back from a Fluxus exhibition, he'd have all the most obvious reasons to go on a ramping rage fit and kill, but Salinger, please...)
Thelonius Monk, John Coltrane and other Free Jazz trend setters - they were in it for the gig and for the fun. Both died of old age.