An excerpt from the Screwtape Letters:

Men are not angered by mere misfortune but by misfortune conceived as injury. And the sense of injury depends on the feeling that a legitimate claim has been denied. The more claims on life, therefore, that you patient can be induced to make, the more often he will feel injured and, as a result, ill-tempered. Now you will have noticed that nothing throws him into a passion so easily as to find a tract of time which he reckoned on having at his own disposal unexpectedly taken from him. ... They anger him because he regards his time as his own and feels that it is being stolen. You must therefore zealously guard in his mind the curious assumption 'My time is my own'. Let him have the feeling that he starts each day as the lawful possessor of twenty-four hours. Let him feel as a grievous tax that portion of this property which he has to make over to his employers, and as a generous donation that further portion which he allows to religious duties. But what he must never be permitted to doubt is that the total from which these deductions have been made was, in some some mysterious sense, his own personal birthright.

You have here a delicate task. The assumption which you want him to go on making is so absurd that, if once it is questioned, even we cannot find a shred of argument in its defence. The man can neither make, nor retain, one moment of time; it all comes to him by pure gift; he might as well regard the sun and moon as his chattels. He is also, in theory, committed to a total service of the Enemy; and if the Enemy appeared to him in bodily form and demanded that total service for even one day, he would not refuse. He would be greatly relieved if that one day involved nothing harder than listening to the conversation of a foolish woman; and he would be relieved almost to the pitch of disappointment if for one half-hour in that day the Enemy said 'Now you may go and amuse yourself'. Now if he thinks about his assumption for a moment, even he is bound to realise that he is actually in this situation every day.

Emphasis added.