There is a whole lot going on in this scene, but I think there are 2 things you should keep in mind:
The power is shifting. Macbeth no longer needs Lady Macbeth to goad him on. He is hiding from her a key piece of this thinking. The first lines of the speech tell you that. Be innocent of the knowledge, Till thou (can) applaud the deed. He is planning the murder of Banquo and he really doesn't want her input. He is telling her that she must wait till the murder is done and then what he has been doing will be apparent. Everybody comments on those lines because it is a foreshadow of many things to come. One of the most obvious is Lady Macbeth's madness.
The rest of the speech has to do with his walk in the path of evil. He prefers night to day, because all is hidden by night.
