Angelina Jolie doesn't "know how to relax".

The Hollywood actress has admitted she's happiest when she's working because she likes being "challenged" but she's also used to being busy because she worked from the age of 14 to help her mother Marcheline Bertrand pay the bills.

Angelina, 49, told Vogue Mexico: "I think a creative person always wants to be growing, and I always want to be challenged, I want to feel that. I think it's also about the relationship I have with myself and feeling like I'm not growing.

"So if I'm working, I'm doing something that's not easy, something I don't understand. I always put myself in situations where I'm not the smartest person in the room, or I don't understand everything that's going on, but I know that so much creativity and human growth comes from being completely uncomfortable, but working hard. So I think that's where I'm happy … "

She went on to add: "I can also blame myself for not knowing how to relax. I can't always take a vacation ... I remember that I worked from the age of 14 to help my mother pay the bills ... I don't ever remember not working or doing something."

Aside from her work in the entertainment industry, Angelina has also been busy raising her six kids - Maddox, 23, Pax, 20, Zahara, 19, Shiloh, 18, and 16-year-old twins Knox and Vivienne - with her ex-husband Brad Pitt and she recently insisted looking after her children is way more important than anything else in her life.

During an appearance on 'Good Morning America', Angelina spoke about playing opera star Maria Callas in new movie 'Maria' and was asked if there's anything in her life that compares to the late star's love of singing and the actress replied: "My motherhood ... It's my happiness. You can take everything else away from me ... Nothing else matters."