Having an OH who has hauled me around the country after jobs and caused many a downsize, it is tough. But cathartic. I have been grateful for the chance to offload large and ugly family heirlooms, but still mourn a few things. Most of our houses have been large, but we have had to exist in smaller rented houses and flats between purchases and I think the biggest upside of a smaller house is the heating bills. Depending on how you feel about housework, you have to stay very organised in a small house and it seems to get dirty and dusty more quickly. But the thought of getting the smaller places clean and tidy isn't so daunting when you feel ill.
We are great hoarders, no matter what size house we live in, and getting dbh to part with anything is tough. I can feel a de-clutter coming on though. I wish you luck, it can be hard, but I have often moved and had to throw even more things out because they don't fit or don't suit the new house. Do as much as you can, a room a week perhaps. I had a huge house once and got rid of a whole large lorry load of furniture in one go and felt really proud of myself!