Giovanni's Room is a book of memories. The narrative itself is simply David remembering the long confused series of experiences that constitute his life. Yet how he remembers things is very telling. What is clear is that he is trying to gain something from looking back over his life. David, in his remorse, feels that he is a prisoner of the past, and hopes that, by telling it to himself in the right way, he can free himself and go forward into the future.
Ever since his mother died, David has come to associate memories with death. The association leads him to view the act of remembering as fatalistic and intertwined with his own grief.
David remembers himself as being innocent, though there is no evidence in the story to suggest that he ever was. In his memory, then, his story is a fall from a state of innocence that never existed.