The Thor actress, who gave birth to her first child with fiancé Benjamin Millepied in June, said that she takes criticism as a personal challenge to work harder.
The 30-year-old, who won several awards for her lead performance in Black Swan, told Psychologies: "I go between confidence and insecurity all the time. I think I won't be able to do something, but I'll do it anyway, because I know that failing isn't that bad.
"With my job, if I mess up, no-one dies."
Portman insisted that she won't let negative comments affect her career. She added: "I didn't get down on myself. I'm the type of person who takes criticism as a challenge to push myself harder and aim higher."
Portman recently endorsed the Foundation for International Community Assistance, whose aim is to provide financial support for mothers.
Watch Natalie Portman's 'Best Actress' Golden Globe acceptance speech for her role in Black Swan below: