It's a serious question, because right or wrong, for so many of us our belongings are part of our identity. Not just in the material sense, but also in terms of holding on to the past. Family heirlooms and kindergarten projects can hold a lot of value to some people. Boxes of school projects may take up a couple hundred square feet in your basement -- a couple hundred square feet you won't have in a downtown loft.
So, what can you part with? If the answer is "most of it," go ahead and start sorting. Even if it's hard, you may be ready to live more simply and part with all the wonderful stuff you've been hoarding.
But we're not just talking about basement storage, here. Most likely, you'll have to part with some of your furniture, maybe even some of your art, and you may not have enough room for the 9-by-12-foot rug you decorated your living room around. If you can't part with these things, you may not be in a good position to downsize.
Plus, some of that furniture will have to be replaced, which is another factor to consider.