I find that we keep things we should not if:
1. The things are not working for us (like shoes that give us blisters) but we spent a lot of money on them
2. The things have no practical use but have happy memories (like the pamphlets from places we visited and really enjoyed but won't go back to or souvenir shirts with stains or holes)
3. Rocks. Don't ask me why. I am in love with rocks. I must have had 10 pounds of interesting but valueless rocks.
4. Books. Get them from the exchanges,, read them, forget to bring them back.
5. Tools/glue/screws, etc. Bits of shiny things we both buy on impulse but never use and won't be able to find if a miracle occurs and we could use it.
6. Fabric. Gorgeous quilting fabric I would need 2 more lifetimes to use.