Lily Cole says acting is like walking a tightrope.
The model-and-actress, who stars in new movie 'The Imaginarium of Dr Parnassus', says the secret to a believable performance is finding the right balance.
She explained: "The good actor is the one who always has a moment when they nearly fall off."
Lily revealed her co-star, the late Heath Ledger, was an inspiration to work with because he became so involved with his character.
She said: "Heath was totally without fear as an actor. When you see him as the Joker in 'The Dark Knight', or any of the characters he has done, he really lives and breathes the character - he was always totally committed."
The 21-year-old star also revealed Heath - who died from an accidental prescription drug overdose shortly before he finished shooting the movie last year - made her feel comfortable on the film set and calmed her nerves before the cameras began rolling.
Lily told Britain's Daily Telegraph newspaper: "There is no doubt that Heath was a massive support to me. I had done so little and had almost no experience, and yet Heath was really generous.
"He was aware that I was nervous, this being the biggest role I've ever done, and he was making a real effort to encourage me."