How would you summarize Winston's thoughts in part 1, chapter 3 of 1984?

At this stage in the story, Winston has been traumatized by a nightmare about his mother. Winston still feels a profound sense of guilt over how he treated his mother prior to her disappearance, and the nightmare exacerbates this. He has another dream, this time a more pleasant one, in which a dark-haired girl—Julia—takes off her clothes in an act of defiance against the regime.
While performing his compulsory exercises that morning, Winston reflects on a number of aspects of life in Oceania. He cannot remember a time when Oceania wasn't at war; all that ever changes is the enemy. In a world where the historical record is frequently changed to suit the authorities, Winston understands the importance of memory as a means of making sense of the past. He vividly remembers his childhood experiences of war, forced to seek shelter in the London Underground with his mother while the bombs rained down outside. Painful though these memories may be, Winston knows he must hang on to them at all costs; this is the only way he will ever be able to remain faithful to the truth.
By controlling the past as well as the present, the Party controls the minds of the people. For Winston, this is the Party's most awesome, most frightening power. He reflects upon the nature of doublethink, the ability to think two contradictory things at the same time, as expressed in Party slogans such as "Freedom is Slavery" and "Ignorance is Strength." Doublethink is used by the regime to construct a whole different reality, a parallel universe in which everything has been turned upside-down. The Party knows that if it can control people's minds through doublethink, and if it can obliterate the past completely, then it can more effectively present its insistent propaganda as the sole truth.