The following was a consequence not so much of a brilliant insight but more of external circumstances. When we moved into the RV, we obviously didn’t have a lot of space(*), so many things were packed into moving boxes and stored outside in the garden shed.
(*) Although I think if we put everything in the RV in boxes, we’d still end up with quite a few.
We figured, it would be easy to go out and get something in case we needed it.
Surprise, surprise, this rarely happens, because it’s simply too much of a hassle to go dig up that esoteric/useless gadget when other solutions can easily be improvised—fortunately the “I will just drive down to Walmart and buy a new one”-monster is long gone; otherwise this approach obviously wouldn’t work.
This also means that there really is no excuse even for the most ardent “I might need it someday” hoarder and all other things being equal, I think this has made it a lot easier to get rid of stuff.
My suggestion in terms of getting rid of stuff then is simply to put your least used “I might need it someday” in boxes and store them somewhere. Maybe you can do an exchange with someone. You store 5 of their boxes and they’ll store 5 of yours. Then after a year, you can decide whether you still want to keep them around, just in case you might need them some day—or decade.