Angelina Jolie suffered sleepless nights working on Unbroken

Angelina Jolie suffered sleepless nights while filming new Louis Zamperini biopic Unbroken, because she was terrified of messing up the movie and disappointing her personal hero.

The Hollywood superstar fought to tackle the late Olympian and World War Two hero's life story, and admits her initial excitement at landing the directorial job soon turned to worry as she realized how big a task it was.

Returning to promote the film following a bout of chicken pox last month (Dec14), Jolie tells breakfast show Today, "It's a huge responsibility (to take on someone's life story). I lost so many nights... sleepless nights, and so many moments of self doubt, especially when someone is your own actual hero. It's my second film (as director) and it's a huge film."

Jolie, who made her directorial debut in 2013 with the drama In the Land of Blood and Honey, reveals she particularly panicked over how she would make certain action scenes look realistic on film.

She adds, "There were so many things from shark attacks to plane crashes; I've never directed anything like that. I often thought, 'This is too important and this is too big', and, 'I don't know how I got here' and, 'I don't wanna fail, I don't wanna fail.'"

Zamperini passed away in July (14), five months before the film's release. Jolie screened an early preview of her film for him before he passed.