D.M.
Don't go into it looking at the whole house. Look at it room by room. Such as, "Okay, today's Monday, I need to start spring cleaning. So let's start small. I'm going to completely sanitize the very small downstairs bathroom from ceiling to those little bolts that hold the toilet seat on."
Personally that's how I do it. Start with the smallest room, and work my way up. Then by the end of it all, when I'm faced with that last very large room, I can get into, "This is the last one. Let's do it!" mindset.