I couldn't take anything for granted: Charlize Theron on her journey as immigrant in US

She is one of the biggest stars in Hollywood and Charlize Theron credits her success to being an immigrant in the United States of America as it encouraged her to work extra hard to make it big.

The Oscar-winning actor says as a young girl in Hollywood she was aware about the fact that missing out on even a single opportunity can be harmful for her career.

"My dream was to pay my bills and not have to get a second job. I loved having the opportunities I got in acting, and I worked hard knowing that those opportunities could be fleeting.

"I could be on a flight back to South Africa. I didn't have a family in the US; I didn't have a support system here. That drove me - I was responsible for myself, and I could not take anything for granted," Theron told Total Film magazine.

Despite the success she has enjoyed in films, the 42-year-old star says she never feels fully secure as an actor.

"I have never felt that. This is common in actors. There are a few I've come across that have a very healthy ego about their status, but I do think this is an industry where there is such a constant turning of new talent, and if you don't stay on your toes, challenge yourself, people won't want to work with you any more and people won't want to see your movies any more," she says.