What does winston decide are the only things that matter? if confession would not be betrayal, what would be? what would this betrayal prove?

Winston states that the one thing that matters is that we shouldn’t betray one another, although even that can’t make the slightest difference. He explains that while confession is not a betrayal because 'they' can force you to say anything, the main source of betrayal would be to believe the false words. That betrayal would prove your belief and the absence of loyalty.