Macbeth slept well for a guilty man.
Lady Macbeth wondered how her husband could sleep without nightmares, or how he could sleep at all, really.
Even now, as she lay awake, she had to lay with her hands under herself to keep them from shaking. She felt as though she hadn't slept for days, for she couldn't sleep for more than a few minutes before her mind flashed with images of Duncan's bloody corpse and her own bloody hands.
Curse Duncan's face, that which looked like that of her deceased father. It followed her. It would follow her through the castle, appearing in the damp stone as she left her chambers. It would stare at her through the window at night.
Curse Macbeth for making her see the bloody scene! If he had remembered to place the daggers she wouldn't have to know the sight of Duncan's corpse.
Macbeth had been distant towards her lately. Perhaps he was too overcome with guilt to talk with her, perhaps he was simply too busy acting as king to be bothered with her.
Or perhaps he was angry with her for persuading him to kill Duncan.
When she was young her mother had taught her that a woman's job was to build their husband up to be great. It had been necessary, therefore, to advise Macbeth to kill Duncan in order to make him king. In order to make him great. She hoped that Macbeth could see that she was only trying to help him. She hoped he wouldn't blame her for his guilt.
Her own discomforts- the guilt, the nightmares, her bloody hands- were merely small inconveniences. They could be dealt with as long as she had fulfilled her purpose as a woman.
She could deal with laying on her hands at night, she could learn to sleep through the nightmares and ignore Duncan's ghost as it walked beside her in the corridors. She could continue to scrub at the blood on her hands, though it would never come off.
She could live with these things, for at least a little while longer.