Great suggestions, Sue!
Responding now to @ckkk, I'd like to chime in:
My husband and I started downsizing before we bought a smaller home and we STILL had way too much stuff when we moved. The kids had taken what they wanted, including furniture, and the rest was given to Goodwill, Salvation Army, etc. I'm not sure who the author was, but the idea of looking at an item and determining if it makes you feel joy or not, was extremely helpful. I'm not a "keeper" but my husband was. The unnecessary things I kept over the years, being an only child, were mostly of sentimental value, but not necessarily my sentiments. I knew that there were things that meant a lot to my mom or dad. It was easier to part with things when I considered the "joy" aspect, the cost of insuring it, the bother of dusting it, or the uselessness of storing it.
You could concentrate on one closet each week, or one room each week, etc. - whatever works for you. It's amazing how you can feel the "burden" lifting as you have less to maintain. I would suggest that if you have someone who would be willing to physically lift, transport, and deliver boxes or bags of articles in their vehicle every so often, you will not find yourself overwhelmed or possibly injured with the project. Be sure to reward yourself every so often - your efforts bless others and make your life more manageable, too!