I would start by refering to the way that Macbeth describes sleep after hearing the mystical voice that suggests that he will never be able to patricipate in sleep again. Consider the positive way that sleep is described in the following images:
Slee, that knits up the ravell'd sleave of care,
The death of each day's life, sore labour's bath,
Balm of hurt minds, great Nature's second course,
Chief nourisher in life's feast--
Macbeth gives us many images that focus on the restorative powers of sleep and how it heals, refreshes and relaxes humans from the cares of the world. The fact that he will not be able to sleep any longer means he will be excluded from these properties of sleep and unable to find relief.
We can also find evidence of an increasing sense of paranoia, as Macbeth, who was described as such a strong, brave and valorous warrior in Act I scene 2, now trembles at the slightest sound and feels that his life is stained by his deed in a way that can never be washed away:
How is't with me, when every noise appals me?
What hands are here? Ha! they pluck out mine eyes.
Will all great Neptune's ocean wash this blood
Clean from my hand? No, this my hand will rather
The multitudinous seas incarnadine,
Making the green one red.
This quote presents us with an incredibly powerful image exploring Macbeth's guilt and the way that his crime has transformed him completely. He is looking at his hands and the blood on them, and wonders if all the waters in the sea will be enough to wash the blood off them. He concludes that so deep is his guilt, and so terrible his crime that his hands will rather turn all of the sea red rather than be cleansed. Killing his King has had seismic consequences for Macbeth, both psychologically and personally, and he will be a changed individual for ever.