In act 3, scene 2, Lady Macbeth is beginning to regret that she and her husband murdered Duncan to gain the throne, saying "our desire is got without content." In other words, she means that they have gotten exactly what they wanted, the crown, but are not at ease or content with it: it hasn't brought either of them happiness.
This is a significant change for Lady Macbeth. Before Duncan's death, she was absolutely sure she wanted to be queen and did everything in her power to manipulate her husband into doing the murderous deed. She even called on dark powers to "unsex" her and kill her compassion so that she could goad her husband into killing his king.
Now, she is filled with a sense of hopelessness because their situation is so unhappy and insecure. She is beginning to think it might be better to be dead, saying
'Tis safer to be that which we destroy
Than by destruction dwell in doubtful joy
In other words, she is doing an about-face. She is realizing the price of destruction (murder) that...
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