Jake Gyllenhaal says fear is a good ''motivator''.

The 34-year-old star has admitted he was terrified ahead of his role as Billy 'The Great' Hope in 'Southpaw' because he didn't want to look like an ''idiot'' with his limited boxing knowledge.

He said: ''I spent five months training for the movie and I trained twice a day. I figured I'd make five months into 10 months if I did that.

''And I was just basically scared that I'd look like an idiot, so I worked as hard as I could. Fear is sometimes a good motivating thing.''

And despite his initial nerves, Jake is ''very proud'' of the final movie.

He added to Access Hollywood: ''I'm very proud of it. I'm proud of the fact that it's a movie that seems like a boxing film, but really is a family movie about the relationship between a father and a daughter, which moves me so much.

''Everybody worked so hard on the movie. And they worked so hard making those relationships real and I think we made a beautiful movie so I'm really proud of it.''

Meanwhile, the Hollywood hunk previously admitted he felt ''naked'' whilst filming for the action drama.

He shared: ''Even when you're only filming a fight, even when it's a movie, in the ring you feel totally naked.

''It's a strange thing, 700 extras watching.''