I knew not how to answer, or how to comfort her. That she had done a grievous thing in taking an impressionable child to mould into the form that her wild resentment, spurned affection, and wounded pride, found vengeance in, I knew full well. But that, in shutting out the light of day, she had shut out infinitely more; that, in seclusion, she had secluded herself from a thousand natural and healing influences; that, her mind, brooding solitary, had grown diseased, as all minds do and must and will that reverse the appointed order of their Maker; I knew equally well.
– Charles Dickens
Great Expectations, Chapter 49. Miss Havisham experiences agonizing guilt for molding Estella into a cold heartbreaker as part of her revenge mission against men. Pip doesn’t know how to respond to her resulting dramatic meltdown. By metaphorically “shutting out the light of day,” or cutting herself off from the world, Pip believes that Miss Havisham’s own mind had grown diseased.