I used to feel guilty if I didn't use every single thing I bought. Not anymore- here is how I look at it: I got so much joy out of whatever it was that I bought so to me that's worth a lot. I have tons of UFO's- like others who wrote, sometimes I need to put one away for awhile. I honestly think working on just one thing at a time would be boring for me.
So sorry about your sister. Be kind to yourself.