I would say that this is mostly true, but not completely. Instead, I would say that fear cracks Winston's spirit, but then disappointment destroys the rest of it.
Up until he is subjected to the torture by the rats, Winston's spirit is definitely not destroyed. True, he does talk about wanting to see the wrong number of fingers. However, he will never betray Julia. But when he is confronted with the rats, he betrays Julia in his own mind.
I think that this is what destroys him -- the knowledge that he had broken and betrayed her. I think he is so upset with himself that he loses his will to resist.
I think this is quite true, Winston's spirit never was broken, until they threathened him with the rats, I think he really was dissapointed in himself!