"I was really naïve, I think," she tells Esquire U.K. for its March issue.
"I was a young 21. Not green as grass – I was by no means an innocent – but I had faith in the goodness of everyone. I was very open. And that lead me into all sorts of situations that backfired."
"I had no business sense whatsoever. I never read a review or paid any mind to what anyone said," she continues. "It was all about the experience. And that translated to how I behaved outside work."
Miller, 32, says that her reputation beyond the big screen, namely her affair with married actor Balthazar Getty, who has four children, damaged her film career.
"I sabotaged things,” she admits. "I burnt a lot of bridges."
"What was going on in my private life was not an easy thing to read about. People don't want to see films with people they don't approve of in them," Miller says, admitting that the affair was immoral.
"I felt like I had no control over any aspect of my life, professionally or personally," she explains. "So I deliberately disappeared. I was sick of myself, to be honest, or sick of that perception of me. It all felt so f–––ing dirty."
During her break from Hollywood in 2009, Miller performed in After Miss Julie on Broadway, where ex-fiancé Jude Law was also working, and the pair rekindled their romance.
"I had to [reconcile with him]", she says, because their relationship was "a huge part of my life and his life and it ended in a way that was awful. When something ends in a way like that, it's important if you can, in a way, go back and revisit it and either shut that door or create a new room. So it was a very healthy, cathartic experience."
Miller is now good friends with Law and his children. "I love them, madly. Just huge love and respect for all of them," she says.
And as for her own family with actor Tom Sturridge, Miller says she plans to have more children, and that being a mother to 18-month-old daughter Marlowe grounds her.
"I feel really settled. I have a wonderful life. I'm up every morning with a little baby. That gives you incredible perspective."