The 34-year-old actress told the New York Daily News that while she looked at sharing screen time with Smith as an honor, playing his absentee wife in the film did not lend itself to fostering a relationship with the actor.
"Will's a completely lovely guy, but I didn't get to know that," Newton said. "I sacrificed that in order to give him what he needed. I really felt my job was to give Will and give the story what it needed. It had to be pretty rough."
"Happyness" features Smith as a semi-homeless man trying to overcome obstacles to find a better life for himself and his son.
Newton, a mother of two, told the newspaper she had a head start on physical preparation for her character in "Happyness," since she was already thin and exhausted from raising her newborn daughter.
Celebrity Families of 2014 [PHOTOS]