Clutter has no logic. Separate all unrelated items from each other. Rubbish is junk. Basically, clutter is rubbish. Three-quarters of the piles on paper on desks and tabletops are things that just haven't been thrown away yet.
Unfinished business is junk.
Scraps of paper with telephone numbers of people whose calls you haven't returned, bags of clothes standing inside the front door that you haven't given to the charity shop, letters you haven't yet responded to - this is the kind of clutter that's mobile. It follows you around, and if you leave it unattended long enough, it changes from junk into big problems. Indecision turns into junk. Clutter is all the stuff you push aside and tell yourself you'll think about later. Fear of regret often stops people being more decisive or throwing things away.