I feel I've earned it. I worked really hard for a lot of years to get myself out of the poverty I grew up in, into a position of financial stability. My bills are paid, I have no debt other than my mortgage, money is going to my Mom and into savings for my retirement and for emergencies and for my sister's kid's college expenses, and I give to my favorite charity every single month....all those bases are covered, so with the money left over in the budget each month, I have fun. I have no children, and my DH makes roughly the same as I do and we keep separate finances, so I am the only person who should care about what I do with my money (so long as I pay all my share of the bills!)
SO with my "fun money" I buy fabric, I buy books, I save it up and buy fancy new sewing machines, I buy old vintage sewing machines, I buy weird rulers and expensive thread and toy robots. I buy weird old things like chrome percolators and rusty hand tools and Pepsi crates and cobalt bottles and glass doorknobs and boxes of hand-forged nails that all remind me of various people and places from my past and make me smile... I have given myself permission to spoil myself as much as I want and in any way I want, within my budget's limits.
