I feel the exact same way -- there's gonna be some big radiator repair/switch going on soon where I live, and I'm going to pieces about how messy my whole apartment is, will I manage to clean up in time, etc. However! I've worked in that position myself, and you know what? I didn't give a damn. As long as no one is getting hurt due to your messiness (like fishes dying in an uncleaned aquarium or something), it was fine.

Also? Be nice to them! Don't stand around staring as if you're afraid they'll steal something. Instead, offer them something to drink or maybe give them a bag of homemade cookies for their break. People who treated me and my co-workers like that got free work in return.