how does winstons character change throughout the novel?

We are introduced to Winston's bleak reality early on in the book. Winston feels dead inside. He struggles to remember his nightmares just so he can feel something real. He writes in his contraband diary as his only method of therapy and rebellion against the state. After Winston meets Julia, he actually feels alive again. The much younger Julia is sexually aggressive and Winston cannot believe that what he is experiencing is real. Unlike Julia, Winston knows it is only a matter of time before they get caught. This affair, however, seems worth the eventual consequences; at least Winston feels alive for a little while. Winston's final transformation takes place after his torture and "re-education" by O'Brien. By the end of it, Winston is a shell of his former self. His brains have been scrambled and his spirit has been crushed: he looks at the telescreen and realizes that he finally loves Big Brother.

Julia's change was much more straight forward. Julia felt her affair was a game against the party, like a girl sneaking out of her bedroom after curfew. Julia, from what we can tell, had been lobotomized. Her spirit was crushed the minute she was taken from the flat above Charington's shop.