While this is her first time behind the camera, Holmes also stars in the emotional drama as a struggling, impoverished single mother of a teenage daughter who tries to get her life back on track by moving to a small Midwestern town.
"The mother-daughter theme [of] that unending love that you have for your mother and for your child is universal," Holmes told ET during a sit-down interview on Tuesday.
Holmes also said that her own daughter, Suri,
helped her understand the dynamic between her character, Rita, and her on-screen daughter, Ruthie, played by 18-year-old Stefania Owen --which is why Holmes honored her 10-year-old little girl
with a "special thanks" at the end of the film.
"She gets a special thanks for everything, [for] every job I do, because she makes every day great and awesome and better," the 37-year-old actress shared. "I know myself better because of her, so she'll always get a special thanks."
The Kennedys After Camelot star
also opened up about her decision to try her hand at helming a feature film, explaining that she's "always wanted to direct."
"It's taken a long time to take the risk," she said. "I feel fortunate because I have a wonderful support group around me."
All We Had opens in theaters Dec. 9.