In Act III, Scene iv of Shakespeare's tragic play Macbeth, Lady Macbeth (after witnessing Macbeth's breakdown) states the following:
O proper stuff!
This is the very painting of your fear:
This is the air-drawn dagger which, you said,
Led you to Duncan. O these flaws and starts,
Impostors to true fear, would well become
A woman's story at a winter's fire,
Authorized by her grandam. Shame itself!
Why do you make such faces? When all's done,
You look but on a stool.
What Lady Macbeth is stating is that Macbeth is acting like a fool and drawing attention to himself. Her referral to being a woman is another attempt to call Macbeth's manhood into question. She state that a woman doing what Macbeth is doing could be justified, but a man doing it is unacceptable.
As for agreeing with what Lady Macbeth states, I would not necessarily agree with her. She knows that Macbeth is having "issues" with what he has done. His mentality has been called into question by her in the past; therefore, his mindset is not something which she is unfamiliar with. Instead, what I would suggest is that she is pointing out the fact that Macbeth, on the night of his crowing as king, is not making a very good first impression on his followers.
Lady Macbeth is certainly seeing a pattern though. The dagger which Macbeth claimed to have seen, and now the ghost of Banquo, is making Macbeth look like a fool ("You look but on a stool").