Helping Macbeth Cope

So, the night we were with Duncan, I finally convinced Macbeth to kill him.  But now he can't stop worrying about what he's done and how bad he feels about the murder.  I keep trying to tell him that it's not a big deal and he's acting like a child.  I don't understand why he can't see it like I do... it needed to happen for us to be in power.  Now that we have succeeded in this, we can finally rule things the way we wanted to.