The 29-year-old actress was in tears on a daily basis during the gruelling shoot, in which she plays the long-suffering wife of Johnny Cash during his drug-taking hell, and is still recovering from the anguish.
She says, "I finished Walk The Line last September and that was a very rigorous process. There were a lot of dark days dealing with a lot of difficult things.
"A lot of crying. Every day I was crying and upset and saying. 'Johnny, put the drugs down, I can't take it any more, baby.'"