Known for their extensive grueling rehearsals, the Dardenne brothers who co-created Two Days, One Night lived up to their reputations and demanded that Marion Cotillard (“Sandra”) rehearse for an entire month on location before shooting commenced. Such intensive rehearsing allowed Cotillard not only to become very comfortable with the entire cast (most of whom are supposed to portray individuals who have known her for a long time), but it also gave the cast time and freedom to experiment with their performances.

In preparing for her role, Cotillard invested extensive time in concocting an elaborate backstory for her character. Though her character’s life story is never fully detailed in the script or film, Cotillard mapped out Sandra’s entire life even before the film begins. Cotillard told The Atlantic, “I needed some material because there are some scenes where she’ll just burst into tears out of nowhere. This is not something that’s easy to do, and you really need to think about something. Because I never use anything related to my personal life, I need to build the character’s background for that.” As a result, Cotillard came up with her own reasons for why her character was depressed and fleshed out all the details on how her emotional struggles have strained her relationships with her family and her friends.

However, Cotillard discovered that after a certain number of takes, the backstory wouldn’t be effective as motivation anymore, a major concern given the emotional demands of her character, so she would have to come up with new ideas or new stories that would carry her on for the remaining takes.