This quote from William Shakespeare summarizes perfectly how Macbeth starts to feel. He starts to get suspicious of everyone, thinking they all might know something about his deeds; starting with his former friend Banquo. "Our fears in Banquo Stick deep, and in his royalty of nature Reigns that which would be feared" -Macbeth Act 3 Scene 1
Much of Aristotle's moral and political philosophy centres on the idea of a golden mean. This is that the true and moral path is found between the two 'vices of excess'. The virtuous path is found in balance and moderation. For example: courage (the virtue) is found between the vices of cowardice and foolhardiness.