Throughout Shakespeare's works, his plays analyze human nature, and Macbeth is no exception. In the classic tragedy, the protagonist controls his own demise by making bad choices and tricking his conscience. .
At the end of the play, Macbeth realizes that his failure is nobody's fault but his own. Macbeth could, conceivably, have led a much different life, a much happier life. As he thinks back over what happened to his life he realizes that "all of our yesterdays have lighted fools"""(As he sees himself)""the way to dusty death"" (V.v.24-25). How did he end up like this? How could a generally good man turn into a murderer with nothing but feelings of disillusionment and existentialism?.
Early on, although the witches influence him, he acknowledges the control that he has over his actions. He does not have to do anything because of the prophecies. In one of his most intelligent lines of the play, Macbeth shows his early understanding of that control, and wonders that maybe "if chance will have me king, why, chance may crown me without my stir"" (I.iii.158-160). Macbeth had the right idea, sincerely feeling he wasn't going to fall into the trap of believing that others can control the way he acts.
However, this wisdom begins to fade away. As Lady Macbeth pressures him by questioning his manhood, he seriously begins to silence the conscience wailing inside of him by making excuses. Macbeth allows himself to believe that murdering Duncan is destiny, that it must be done, and even that he would be less of a man and a husband if he didn't follow his ambition.
Slowly, Macbeth's brain becomes even more corrupted. He falls into the paralyzing trap of tricking his conscience whenever he can. He tries to destroy the visions of the good inside of him in the form of bloody daggers before the murder of Duncan, and he succeeds. He tries to believe that Duncan is only asleep, and succeeds at that, as well.