Desire and misery

"But while that Tree flourishes she will never come down into Narnia. She dare not come within a hundred miles of the Tree, for its smell, which is joy and life and health to you, is death and horror and despair to her." (spoken by Aslan)

..."I forgot to tell you. The Witch has already eaten one of those apples, one of the same kind that Tree grew from." (spoken by Digory)

"So we thought, Aslan," [Polly] said, "that there must be some mistake, and she can't really mind the smell of those apples...she ate one."

"Child," he repied, "that is why all the rest are now a horror to her. That is what happens to those who pluck and eat fruits at the wrong time and in the wrong way. The fruit is good, but they loathe it ever after."

"Oh I see," said Polly. "And I suppose because she took it in the wrong way it won't work with her. I mean it won't make her always young and all that?"

"Alas," said Aslan, shaking his head. "It will. Things always work according to their nature. She has won her heart's desire; she has unwearying strength and endless days like a goddess. But length of days with an evil heart is only length of misery and already she begins to know it. All get what they want: they do not always like it."

-- from The Magician's Nephew by C. S. Lewis