Wow Stayseeliz...what a great list of questions. I like it. For me...you just have to come to a point where you "get over it".
I had things that I was doing that same thing with... "well, I might need it"..."or I could let so and so use that so I better hold on to it". I have a nice DH who helped me see the stupidity in those statements.
I guess with the bigger items like my bread machine, my cookware, etc. I kept it if I knew I would use it, like Stayseeliz said, within the next 3 months. If not, it was given away. When in doubt, just get rid of it. Even with my bread machine, if I gave it away, I could get another one down the road. And probably for $5 at Goodwill! So I ask myself that question a lot...if I did need another one, could I get it?
You asked why decluttering is so painful...and for me it was because I felt that certain things represented me at different parts of my life. Like that picture frame someone gave me for my wedding. I didn't even like the frame, but it reminded me of the feelings I had at that time in my life. Or the figurine that my mom gave me when I miscarried...I think the figuring itself is kind of funny looking and I never even displayed it, but I kept it because it reminded me of the emotions of that time. So I did what several people have said to do, and that is to take a photo of that special belonging, file it away, and then give the stuff away. It was very freeing. You really have to examine your heart and find out why you are keeping things. Was your family poor growing up? Are you keeping things to show that you do have "stuff" now? Does being a packrat run in your family? I know it does in mine...I'm trying to break the cycle!
Don't get discouraged...once you start getting rid of stuff, you will instantly get motivated and start getting rid of everything. It becomes an addiction!
And just keep saying over and over as you clean:
"I have no emotional attachments to my material possessions...I have no emotional attachments to my material possessions..."