Charlize Theron says being an immigrant in America encouraged her to work extra hard to make it in Hollywood.

The Academy Award-winning actress is currently one of Hollywood's most in-demand stars, but Charlize has admitted that her original ambitions as a performer were much more modest.

She explained: ''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.''

And despite the success she's subsequently enjoyed in Hollywood, the 42-year-old star has confessed to never feeling fully secure as an actress.

Charlize - who has starred in hits such as 'Atomic Blonde' and 'The Fate of the Furious' - told Total Film magazine: ''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.''