Offred, the protagonist of Margaret Atwood's The Handmaid's Tale, is similarly unable to divorce her sense of self from her past experiences. In the society of Gilead, identity is also attached to purpose. As a Handmaid, she is no longer considered a person, only a vessel which those in power can use to produce heirs. If she is unable to have a baby, even that degrading purpose for living will be taken away from her, and she will become an Unwoman. Her only option for escape seems to be suicide, basically "unwomaning" herself before others can do it to her.
Not having read Atwood's work, I could try to offer up some clarification on Styron's protagonist. Sophie understands her own conception of self in light of historical reality. That is to say, she understands her sense of identity through the historical experience of the Holocaust, and the choice she was forced to make. Analysis of why these conditions arose and why she did what she did help to form the basis of her identity. Naturally, there can be little in way of rational explanation behind these actions, which end up making her consciousness of identity an incoherent one. It is here where the greatest statement might be made about Sophie's (and our) relationship with history. It is completely and painfully incomplete. Sophie's identity is bound with her experience at Auschwitz, as inescapable as the number branded on her arm. The struggle to try to understand the basis of such an experience, why she lived and her children died, why she could not be more resistant, and why she is cursed with never fully understanding the critical moment of choice are all realities that are a part of her consciousness and our own historical consciousness. Sophie is unable to divorce herself from her history and thus her consciousness of identity is unable to find any hope or glimpse of totality.