Stars, hide your fires!
Let not light see my black and deep desires.
--Macbeth, Act I, scene iv
In this quote I believe that Macbeth is feeling bad about wanting to kill Duncan so he wants no one or the stars to not know about how he feels or what he wants to do.
I am in blood
Stepp'd in so far, that, should I wade no more,
Returning were as tedious as go o'er.
--Macbeth, Act III, scene iv
Here I believe that Macbeth is wishing he hadn't killed all those people to become king. He feels like he is surounded by their blood because he can't get their deaths out of his mind so he feels surounded by that and so surounded by their blood.
If it were done when 'tis done, then 'twere wellIt were done quickly: if the assassinationCould trammel up the consequence, and catchWith his surcease success; that but this blowMight be the be-all and the end-all here,But here, upon this bank and shoal of time,We'd jump the life to come. But in these casesWe still have judgment here; that we but teachBloody instructions, which being taught, returnTo plague the inventor: this even-handed justiceCommends the ingredients of our poisoned chaliceTo our own lips.
--Macbeth, 1. 7
When Macbeth says this I think that he thinks that he killed Duncan to fast with out thinking. Maybe at first it was great and life was great but as time went on it really wasn't great, and the one that causes pain recieves pain.
I am afraid to think what I have done;Look on't again I dare not.
--Macbeth, 2. 2
Here Macbeth says he feels bad and doesn't want to think about it.