The Forgetting Sarah Marshall star took on the title role in the 2011 remake of Dudley Moore's classic 1981 comedy, about a drunken playboy set to inherit a fortune, but it was widely panned by critics.
The funnyman admits his inexperience combined with his over-enthusiasm for the project was a recipe for disaster, and reveals he was hurt by the negative response.
He tells The Sun newspaper: "I didn't know a lot about script construction. I know more now. I was just embracing things enthusiastically. I thought I could do anything. I felt a little bit bruised (by the reaction). I felt I'd made a mistake."