Afraid of the Mess.... Help!

So today is the day I decided to start on my office. I have a large inbox that is now filled with stuff off the top of my desk.

I haven't touched what's on the other surfaces, in the drawers, etc.

I'm afraid of the mess I'm going to make!

I'm SO tempted to just take care of the desk first, and then move forward, instead of doing it all at once.

Somebody who had a big job of this, quick -- tell me it works so that I can keep going!

(The irony is, the office is a mess to begin with, thus the big piles that are going to start growing. The problem is I'm going to have to stack the stuff in the hall or living room, and am afraid of the mess taking over the rest of the house. Yikes!)