Angelina Jolie feels lonely because of her dedication to her work

She told People magazine about their shared traits: "I don't want to speak too much about it because it's too personal, but there's definitely a loneliness and a work ethic," she says of her connection to Callas. "I may be many things, but I'm a very hard worker, right?

"I'm an imperfect person, but I work very hard and she does."

And Angelina doesn't know if she or Callas would see themselves "as anything but a performer and a worker who has a job to do," and thinks they are both "probably very hard on ourselves."

The Oscar-winning star - who has six children with ex-husband Brad Pitt - previously admitted immersing herself in opera training for the movie was the "therapy" she didn't realise she needed.

Speaking to WSJ. magazine, she said: "Pablo (Larraín, director) expected me to learn, to really sing... to understand and study opera, to immerse completely and do the work.

"But it was much more than that, it was to understand Maria Callas and be able to play the character.

"I had no idea how much I was holding in and not letting out. So, the challenge wasn't the technical, it was an emotional experience to find my voice, to be in my body, to express.

"You have to give every single part of yourself... everything that you've got."

The 'Maleficent' star spent "months" working on her vocals.

She previously said at the Telluride Film Festival: "I had seven months of opera classes, great teachers and Italian classes, and a supportive team that were going to help me."

Despite this, Angelina still felt anxious about singing when the time came to do it.

She said: "I was so nervous that morning I was out of my mind."