The Irish star has been sober for seven years and admits he was ""cooked"" for much of his Hollywood breakthrough, but he worried that booze gave him the edge he needed for demanding roles - and he'd be lost without it.
The Miami Vice star says, ""I was terrified that whatever my capacity as an actor was... however little or large it was, it would completely disappear and that I wouldn't be able to... I ascribe to the notion that to be able to express yourself in an artistic form in life you have to live in perpetual pain - and it's nonsense.
""There's enough pain in the world that if you've any sensitivity to you can kind of... feel, you can experience... There's enough pain in the world that you don't have to live in it to represent it in some artistic way.
""When U2 wrote Sunday Bloody Sunday, the lads didn't live up in Belfast, but they lived on the island and they knew what was happening up there.""
And Farrell admits he's having more fun sober.
He tells U.S. chat show host Ellen DeGeneres, ""I'm really grateful. It's really lovely to be present in my life... It's actually more fun.""