She struggles to remember what kind of person she was when she was younger and was visiting a certain city or state.
Some of things she thought or noticed back then baffle her, other things ring true. She finds the reviewing process of her notes to be very revealing. They show her things she long ago forgot, or never really knew.
She really seems to enjoy the topic she is writing about. As a journalist, it is clearly important for her to keep lots of notes, but she also believes in the process in a personal sense too. Didion writes, "I think we are well advised to keep on nodding terms with the people we used to be, whether we find them attractive company or not." This is a very powerful idea, which is probably worth ten self-help books. Keeping a notebook or diary, for me, is an important way to stay connected to the world around me and the person who I once was. It is very easy to lose track of one's identity in this fast-paced world. Didion seems to have found the solution: take notes and review them every few years in order to remember who you used to be.