A successful totalitarian state cannot accommodate private loyalties, since private loyalties will often trump loyalty to the Party. Because sex and family create private loyalties, the Party must somehow control these social acts and constructs. Thus, the Party brainwashes children to believe that sex is despicable, unpleasurable, and merely a means to create new Party members. Chastity is encouraged, sexual drives become repressed, sex is seen as a "duty to the Party," and all potential private loyalties are thus eliminated.
The fickleness of Winston Smith’s varicose ulcer is indicative of the Party’s successful sexual repression of its constituents. Sexual repression is the Party’s most potent tool of power and control.