I had plans to live in a van/tiny house, so I did a fairly extreme downsizing.
There were a couple of moves where some big stuff, like junk motorcycles were purged.
And then a divorce, relocating to a studio apartment. Lots of stuff purged, but way to much stuff stored.
Back into a full-size house, I moved all my stuff back in with me. We decided to downsize drastically for life on the road and found out most of our stuff was worth nothing.
Round 1) Sell stuff of known value on ebay and CL.
Round 2) Sell stuff at yardsales, and give away stuff to friends and family.
Round 3) Goodwill, Salvation Army, free outlets.
Round 4) Dumpster/scavenger guy down the road.
We had a bunch of books -- thousands -- which we listed on Amazon used books, using a seller account. We priced to sell, so at a price where it would appear on the first page of listings. If the book was mass market or a book where there are millions in print it wasn't worth our time listing them or the time and material it would have taken to ship them out.
Don't overvalue your stuff. Your stuff is only worth what someone is willing to pay for it, in the time-frame in which you need to sell it.
Do you own your stuff, or does your stuff own you...?
And BTW: I still have too much stuff...