It's harder to mentally imagine living in a tiny condo or apartment in an expensive metropolitan area when you've never been constrained with such a small space, but even if you're currently a packrat living in a huge cheap place, one can benefit from occasionally asking, "How much is enough?"
According to Unclutterer, to avoid accumulating large piles of unnecessary crap, you must go through a cycle of sorting and evaluating objects by function, then determining whether or not the item is worth getting rid of:
Evaluate product types and decide what we need and what inspires us. Is it necessary that I have three hammers? Is one hammer enough to meet my family's needs? Is more than one hammer a distraction (clutter)? Is having one pair of scissors in the sewing supplies, another pair in my office desk, and another pair in the kitchen the best solution for our family? Do I have more yarn than I could possibly knit in a year or in a lifetime?
As with any type of framework, the end result is entirely subjective and depends on your needs as a person. But surely, you don't need those 3 extra keyboards, the mountain of Ethernet cords sitting in your garage even though you've already gone completely wireless, or those box of floppy disks taking up space in your desk drawer, do you?
[Image by Wiq3000]