Ally, first let me say you are not alone in your struggle. Letting go is hard...but look at your progress! Look at the courage and strength you've dug deep to find. See the freedom you've found in baby step decluttering. Your honesty with yourself about the UFOs and your desire (or lack thereof) to finish them is so important.Many of us fool only ourselves into thinking "I'll get to it someday" when the gut-level truth is, that project no longer does anything for me. I may not be finished sewing it, but i AM finished with it! It might just be in a stage of dineness where someone else may want to pick it up. But if not, that's not your problem. Remember it doesn't have a pulse, it has no feelings, it has no value other than what someone ascribes to it. Hoarders or collectors or keepers (call them whatever you like) tend to anthropomorphise everything -- that is, to give human characteristics to nonhuman things.
If if that's one of your tendencies, stop. Retrain yourself to think "it's just a thing. It's not a life." One of the hardest things I had to learn was that getting rid of an object does not mean I'm getting rid of the memory or getting rid of the person who gave that object to me. But I can assure you, once I started letting go of stuff and just keeping memories and people dear, I was so liberated. I should say it's an ongoing process .
Burden or blessing? Ask yourself which it is with everything you touch in your sewing room. Don't overthink it. Drop your burdens --you've already begun. Keep the blessings.
One more thing that helps is to take pictures of your progress. It will give you a visual pick-me up to see bags, boxes, bins, stacks, piles of burdens gone! I'd love to see your progress!