The breakdown of the novel was described to me in a very easy to understand way in my high school literature class (many years ago).
Orwell broke the novel into three parts, which shows Winston Smith's growth (and possible regression) throughout the novel.
Part one focuses primarily on Winston's initial realization and rebellion against his society. This rebellion is made known only in Winston's thoughts. (Rebellion in Thought).
It is in Part Two that Winston begins to show a physical rebellion to big brother. Winston begins to take charge of the freedom he feels society should have: freedom of speech, thought, and action. He dares to fall in love, only to have it all take from him. (Rebellion in Action).
In Part Three, Winston falls to the power of the totalitarian society in which he lives. He simply is not strong enough to take on the entire nation as an individual and regresses to the brainwashing, and "love, of "Big Brother." (Failure of Rebellion to Totalitarian Power).