Hamlet is talking about his duty now to avenge his father. his mother is "stained" by Claudius. He is giving out to himself about his procrastination and lack of action. Hamlet doesn't understand why he cannot just put his mind to the side and go and kill Claudius. Hamlet then after this quote goes on to "my thoughts be bloody or be nothing worth". where "let all sleep" changes and becomes action. and changes into, ima kill claudius and avenge dad