The 'Iron Man 2' actress - who has children Apple, five, and Moses, four, with Coldplay frontman Chris Martin - says her main priority is her family and she is careful about how she balances her life so as not to jeopardise her happiness.
She said: "I worked so much in my twenties and then I had these two beautiful kids and I just wanted to be home with them. It's probably not the best thing for your career but my kids are my priority.
"I could throw myself into my career and then I'd probably lose my marriage.
"You have to be mindful of your balance. My family is super important to me. You don't want to get too career orientated and lose that."
The 37-year-old star claims she learned how to balance her life by looking at the example set by her mother, actress Blythe Danner.
She explained to New! magazine: "My mother made a similar choice, for a long time. So that was my model.
"I love what I do but their needs are more important than my needs. I don't need to be doing three films a year and be the biggest star."