We're slowly decluttering our home, focusing on a different part of the house (a closet, a bookshelf, etc.) every weekend. Yesterday we cleared out Ed's electronics closet, which was practically archaeological; nearly everything got thrown out, including a plethora of wires whose uses were unknown, or for electronics that Ed no longer had. And in some cases, the electronics themselves were horrendously out of date, like the old digital camera that has fewer megapixels than our cell phone cameras. Digital cameras are relatively inexpensive now that if we wanted one - I wouldn't be averse to buying a more up-to-date model at some point - it wouldn't break the bank, and the technology would be a lot better than any of the three or four digital cameras we've gotten rid of in the past year. We also got rid of a scanner, hard drives, floppies, CDs with games and other software (all of which can be downloaded), manuals for hardware that hasn't been owned in years, and other equipment that simply won't or can't be used.
There's a lot of space in that closet, now.
A few weeks ago we went through Ed's walk-in closet, and eliminated at least 2/3 of the clothing he hadn't worn since before we got together - sweatshirts from college, an almost 20-year-old leather jacket that hasn't been worn (and that hasn't fit) in more than 10 years, etc. It can be difficult to throw these things out or donate them, but if an item hasn't been worn or used in a certain amount of time, out it goes.
Ed has more elements of packrat-ism than I have and I think has more difficulty going through things and cleaning things out; it seems to take more out of him than my cleaning out my own belongings does for me (to be fair, I have trouble getting rid of books), so taking one part of the house at a time makes things manageable.
I don't like owning things for the sake of owning them; I prefer simplicity, experience over ownership of things. If something has actual value, has use, or is an heirloom, that's one thing, otherwise out it goes. Even then, there's a fine line.