The 38-year-old actress plays an alcoholic singer in Country Strong and said that the power of her addiction to cigarettes helped her to understand why and how people abuse drink and drugs.
She told Harper's Bazaar UK, 'I understand how you can do something bad for you because I smoked forever. I smoked even when my dad had throat cancer.'
But it was friend and Iron Man co-star Robert Downey Jr that helped her kick the habit by making her see how her smoking could affect her family and friends.
'I was like 'I know this is probably going to kill me, but I'm going to smoke it anyway'. But I didn't understand wrecking other people's lives, and then kind of just waking up and tying your shoes. So he helped me figure that out,' she said.
Her father Bruce died after a long battle with the disease in 2002.