What sane person could live in this world and not be a little crazy

I still don't think he's insane. He became a little a-wall after killing Banquo, he couldn't control himself. That's only because he let his conscience get the best of him and it started controlling him. He began seeing the ghost of Banquo and started tripping out in front of the lords and Lady Macbeth, and here is where we see how amazingly evil she is. She is perfectly fine, should have won an Oscar for that one. She was telling him to balls up and get a hold of himself, she even enjoyed herself drinking and partying it up knowing that Banquo was being killed.