I think cancer - I'm not an expert or a doctor - but I think cancer is the result of undigested dreams and forcing yourself to do something that is not distinctively you.

In a way, the world?view of the Party imposed itself most successfully on people incapable of understanding it. They could be made to accept the most flagrant violations of reality, because they never fully grasped the enormity of what was demanded of them, and were not sufficiently interested in public events to notice what was happening. By lack of understanding they remained sane. They simply swallowed everything, and what they swallowed did them no harm, because it left no residue behind, just as a grain of corn will pass undigested through the body of a bird.