http://www.salon.com/life/since_you_asked/2011/01/25/alcoholic_sister/index.htmlLeaving "stuff" and not letting it go, is another form of staying attached to the person.
Think about what you need more: a sweater, shoes, a box, an electric piano manual...
Or your serenity and peace of mind. (You can find the piano manual on the internet. A sweater? NEED sweater? NEED shoes? I believe you can let them go. To make sure there is no lingering involvement, communication, attachment with M, which is not healthy for you...)
Yes, you are enduring sadness, as you learn to not fuse with people. As you replace fusion and fast attachment with Lupita-love, Lupita-therapy, Lupita-creativity, Lupita-courage, Lupita-NEW-thoughts...this sadness will change.
Sadness is not your permanent emotion, only your habitual one.
What about friendships where you do not spend the night together?
What about meeting people for lunch, for a weekend daytime walk, for a class or art event you attend together?
xo
Hops