Smith struggles to maintain his sanity and his grip on reality, as everything (media, gatherings, food, fitness, etc) is controlled by the state including history which is being rewritten by the "truth" department to remove "inaccuracies". The main theme is around the regime's overwhelming power and influence while persecuting individualism and individual thinking on any level.
During the movie the party is up to it's tenth version of the Newspeak Dictionary, which appears to be getting thinner. One of the dictionary's aim is to reduce the words available to the people to use in order to express their feelings against the party.
There is of course control over relationships by the party, any that are non sanctioned are crimes. Winston does of course meet a fellow worker Julia (Suzanna Hamilton), and they do of course commit "sexcrimes" with each other. This cannot continue, hence they are captured by "Thought Police" whereby they are both interrogated and brainwashed.
One of the questions that the film poses is can the human spirit or desires like love be fully controlled? The movie is worthwhile watching, and considering that it was written in the 1940's is still very relevant in the questions it asks.