Let's take a coffee break, shall we?
I wish I could, but I can't.
What keeps you so busy? You've been sitting there for hours. You've got to walk around. You just can't stay on the computer forever.
Well, I am up to my neck in work. I've got to finish this report. Sarah needs it by noon. I don't want to be scolded if I can't finish my work by the deadline.