His inner-strength, he acknowledges, had been forged early on. And, in a way, out of necessity. “I stopped doing drugs when I was 20. I was finished with drugs before Nirvana even started. And I didn’t do hard drugs. I saw it as something that would make everything a little more difficult.
“I also know myself well enough to keep out of that. As soon as I get my face in a pile of coke, it’s game over – teeth out, money gone. You see the way I drink coffee! It’d be all over!” he laughs.
“Plus, I’ve seen it before – before I was in Nirvana I knew people who had OD’d. I love to play music. So why endanger that with something like drugs?”
http://www.telegraph.co.uk/culture/music/rockandpopfeatures/8450113/Dave-Grohl-interview.html