A self is not discovered but deliberately constructed through repeated acts of will: choosing values, disciplining desires, and resolving to become a particular kind of person. The journal becomes the tool of this construction, a place to record resolutions and audit whether one is living up to them.
The private notebook is not merely a record of experience but an instrument for creating a second self: by writing one does not just express what one is but constructs who one intends to become. The journal lets a person be candid in a way impossible with others, making it the site where identity is rehearsed rather than reported.
At seventeen, while a student, Sontag met Philip Rieff and married him within about ten days of meeting, a decision she later framed in the journals as an act of self-betrayal and near-suicidal haste. The marriage is recorded less as romance than as a case of a young intellectual submerging her own development in another's.
Sexual and erotic longing is treated not as a distraction from intellectual life but as data revealing who one actually is, including an awakening to desire for women that reorganizes her sense of self. What one wants, read honestly, discloses the shape of the person one is becoming.