Answer:
First of all, Goldstein is presented as physically repulsive. Winston tells us, for instance, that he has a "face like a sheep," a "silly" nose and an overall air of self-satisfaction
Winston's had a hopeful belief in the Brotherhood, this was uncharacteristic for a man as fatalistic as he, actually contributes to his sense of impending doom. As with his first act of rebellion, he knows that his desperation to wriggle free of Party control will eventually get him caught.