I love self-care days. Buy yourself a new color of OPI for your toenails while you're at it.
I like to go to the thrift stores, and I will spend a couple hours in search of who knows what. I usually have something in particular I need that I refuse to pay $50 for new, but that I'll gladly pay $4 for at the thrift store. Lots of brand new clothes, never-been-worn. Coffee makers, all kinds of things. There must be 15 thrift stores within a half hour from me. It's fun.