I'm primarily focusing on books right now, because that's my biggest area of hoarding. I run my finger lightly along the shelf (shelves. Oodles of them.) And I pause here and there and a) try to remember what the book was about, and b) remember whether I liked it. Surely I must have, if I've kept it all these years. Some of them are dear favourites which I won't part with until someone pries them from my cold dead hands. But some of them, though they gave me great enjoyment, are probably not going to be re-read and couldn't be called my favourites. So one by one I've been slipping them into the book exchange shelf at work for others to enjoy.
Some are in perfectly new condition and I could probably sell them on eBay and recover some of the cost. But I fear if I held onto them long enough to run the auction and package them up and then have to walk them down to the post office, I will chicken out entirely and end up keeping them. Better to let go quickly, without prolonging it. Because---contrary to Buddhist philosophy---I really am attached to some of these. Not just the words within them, but the actual feel and look and scent of them.
Other than books, there's really not a lot else to downsize. I've been pretty frugal over the years. But books are my passion. Choosing from among them is like trying to choose which child to let leave the home.
Maybe, like the children, the books will come back again...