My mother moved from her house to a one bedroom seniors rental, and since she had a sister who was close to a hoarder and had already moved to one of these one bedroom units she was so afraid of cluttering hers up the same. (Not really a problem as my mother was always a neat freak, but anyway..) We helped her take items over that she really wanted, then if she had room, would take a few more, and a few more till she had everything she wanted. Family took a few things but not really that much that we wanted. After about a month living in her new place, we all went through the last of the thngs left , and then had a sale to get rid of the rest of the stuff.
This gave her the time to really think about what she wanted/needed in her new place, and gradually get comfortable with not having some of her things, with the option still there if she changed her mind.
She's been living there for about 10 years now, and still gets rid of things she doesn't use to keep the clutter down.
Wish I was more like my mother!!
Laurie