Mila Kunis lacks confidence

London: 'Friends with Benefits' star Mila Kunis says she is always nervous she will get fired because she lacks confidence.

The 28-year-old actress said that she is never comfortable on the sets until she is half way through the shooting schedule, reported Stylist magazine.

"I am nervous every day I go to work that I'm going to get fired. It's only once we pass the halfway point through production that I'm like, 'Oh well, they aren't going to fire me now, it's too late.'

"Otherwise, whether you have to be funny or mean or angry, whatever the character is, it is incredibly nerve-wracking to go to work because acting is based on opinion," she said.

Despite her highly-acclaimed role in 'Black Swan', Kunis still considers herself an imposter and doesn't understand how she became famous.

"I have no clue how I got here. I feel as if I tricked a lot of people and I don't even know how," she said.