It's more than a week since I started trying to move some of the accumulated "stuff" out of my life. I've gotten almost 140 different things out of the house (some to the trash, others into recycling, still others have gone to thrift shops and libraries). Listing the items has helped in two ways. It's satisfying to see how much has gone (though truthfully, I can tell by looking at the house, noticeably less cluttered), it's also helpful to see the patterns in what tends to accumulate. Choosing to count "classes" of stuff rather than total items has had the benefit of letting me discern once about the need for an item and then each new encounter doesn't require repeating the process. Crib sheets can just go when I encounter them, now that I've firmly decided that are not needed in our lives (I've found them stashed in three different spots so far...). Like reverendmother, putting a specific boundary around the project puts a bit of stress on it. When I didn't add to the list (though I was still clearing clutter) for a couple of days, anxiety crept in at the edges.
The clutter has been a stressor for a long time. I spend far too much time looking for stuff, and having to mentally track it all takes energy.
So far it's been a success, so even if I don't get to 400, both my house and my brain feel less cluttered.