(Cover) - EN Showbiz - Natalie Portman says she it will probably take five years to realise how much her new movie affected her.

The actress plays ballerina Nina Sayers in new drama Black Swan and her performance has been lauded by critics. There is even speculation she could receive a best actress Oscar nomination, but despite the praise she has received, Natalie admits making the movie took its toll on her mentally and physically.

The star had to undergo hours of ballet lessons to prepare for the role, then worked 16-hour days with minimal sleep to shoot the film.

She had to take a break from acting after the movie had wrapped to recover, but admits the full impact of the process might not have hit her yet.

"I definitely felt both physical and mental aftershocks from the experience, because it was the first thing I've ever done that was this physically demanding on top of an emotionally demanding part," Natalie explained to MTV News. "And it's great. I mean, the kind of discipline that it demands also puts you in that space for the acting part. But yeah, it affects you in ways. I'll probably figure out how it affected me in, like, five years. I'll look back and go, 'Oh, that's why I did that and that and that.'"

The 29-year-old beauty felt a deep connection to her character because they have both been the subject of scrutiny about their performance and looks. Natalie admits that in her early 20s she lacked self-confidence and worried too much about what other people thought. As she approaches her 30s she has learnt to focus on her own happiness and to ignore other peoples opinions.

"It's about breaking out of a system where you're easily replaceable by the next girl who looks like you. And I feel like my 20s were about that, and probably into my future, I'm sure it'll continue being that way, Natalie added.

"But the older you get, the less you care about what other people think and the more you just want to be your true self and express your true self." (C) Cover Media