One of the basic tensions underlying Long Day's Journey is the conflict between fate and free will. All the characters want to change their lives, but at the same time, they can't get this depressing fatalism out of their heads. The play's matriarch sums it up well when she says, "None of us can help the things life has done to us. They're done before you realize it, and once they're done they make you do other things" (2.1.76). We should point out that the idea of fate is different here than in a Greek tragedy. The characters aren't pawns of the gods. In Long Day's Journey Into Night, the word "fate" is short hand for family history and past mistakes. Each character struggles against the tides of the past. Even though they aren't battling divine will, they are all in least in some way shaped by forces that are out of their control.
In conjunction with her efforts to dull her pain with morphine, Mary resorts to a fatalist, inflexible philosophy of life that allows her to write off any blame she would otherwise assign to herself or others.
All of the philosophizing and book learning that has preoccupied Edmund has only made him more inept in practical matters.