He said: "[My life mantra is] don't be a pu**y. Basically, that's the best thing you can ever think. I've had so many occasions in my life where I've acted like a pu**y and regretted it. Have you seen that Mike Tyson documentary? That bit where he says he'd defeated the guy before he's walked into the ring, it's the same thing.
"With acting, I was always so scared. But you get to the point where you realise it doesn't matter."
The decision to be braver led him star as a billionaire playboy in new movie 'Cosmopolis', but he admits it is still a struggle for him to always feel completely comfortable.
He added to Shortlist magazine: "Oh man, I was terrified on 'Cosmopolis'. There was a sex scene and I was cringing. The girl was really comfortable with her clothes off - and I'm not. She took all her clothes off and I was just sitting there going, 'Um, I haven't got my 'ball-sack' on.' F**king amazing."