I think it comes from spending the night at my grandmother's house with little notice and she would put me in one of her giant granny nightgowns. We were twins and I felt so loved!
I can see then why you love wrapping yourself in a "giant granny." How about slipping a lavendar sachet in your nightgown drawer so that when you slip into your favorite, soft, giant granny, that it smells lovely, too. It's time to start treating yourself like the special lady you are. What do you say?