I miss not working and being out and about. I miss not being able to do the things I used to do, normal things like shopping, gardening, etc. I miss being able to clean my whole house without having to take breaks or break it up in to days. I too miss the spontaneity of life.
Jules had a great answer as well. I miss having the confidence in my physical ability to do normal activities. I don't have confidence at all in my abilities (physically and cognitively).
I miss my shoes!!!! I miss wearing pretty heels and dressing up. Shoes can make an average pair of jeans look extraordinary, a "humble" pair of pants or capris look dynamic, etc. My shoes meant so much to me and I now mostly wear flip flops and flats.