The following is now a cliche, but it is a cliche because it is so true
^God, grant me the serenity to accept the things I cannot change, the courage to change the things I can, and the wisdom to know the difference.
I do not know whether you have lost your stuffing after illness or after one of life's tragedies and disasters, but restuffing starts with putting small handfuls of stuffing into the small fiddly places and gradually getting to the point where you can put it in in bigger handfuls.
Lots of suggestions up thread, but I think the most important is to get out of the house everyday if you can. I do not know whether you live in a town, city or rural area, flat or house, but just get out into the fresh air. Sit in the garden (well wrapped), walk down the street to the corner shop, saying hallo to people as you go. If nothing else open a window wide and breath in deeply.
Then follow up any or all the ideas, other people have given you.