“But I might need seven sleeping bags one day.”
Solution: Everyone fears tossing something out only to realize―six months, a year, or five years down the road―that she shouldn’t have. Keeping things around “just in case” makes people feel safe. If your main problem is an overflowing closet, try the “packing for a trip” trick. It goes like this: You’re packing for a month’s vacation―you’ll need both dressy and casual clothes, for warm and cool weather, and you can fill two big suitcases. Then take all the other things and place them on a rack in your basement or attic. If you want to wear any of those exiled clothes in the coming days, grab them. But as the months go by, you’ll be shocked at how few of those clothes you need or even think about. From there, it’s a baby step to a Goodwill bag.
Still have separation anxiety? Box up the stuff you’re not quite able to part with and write on the outside, "Open in August 2011"―or whatever date it will be one year from now. Then tuck it away in your basement, attic, or storage facility. If a year from now you find that you didn’t miss the items, it will be much easier to part with them.