As Winston wrote 2 + 2 = 5 he remembered Julia. He remembered the woman he had loved.
He remembered Julia telling him that; ‘They can’t get inside you,’ But she was wrong, they could get inside you. They could get into your brain and control you.
At his torturer, O’Brien had told him during the worst of it; ‘What happens to you here is for ever.’
That was true.
There were things, your own acts, from which you could never recover. Something was killed in your breast: burnt out, cauterized out.
He felt, without giving names to feelings and thoughts, what had happened to him during the torture.
Winston doesn’t admit, not even to himself what happened. He shoves thoughts which could disrupt his current moment, out of his mind. It isn’t hard. He has truly been brainwashed.