I always tell my husband, "Hobbies are only fun if you do them when you feel like it." Don't force yourself. Things changed, and you're rolling with it. When you have free time, you need to do whatever feels relaxing to you in that moment. Don't turn quilting into a chore that must be done. Those quilts you haven't made yet will still be there when you're ready to start again.
I'm sorry about the pain your daughter and her children must be going through right now. Sometimes divorce is the right decision, but it's never an easy or painless one.