I take it. I schedule it.
When my son was little, I had several "days off" per month, either on a weekend or during the week (even better - fewer crowds!). My husband works at home so we just scheduled a few days off a month for me. I started by doing errands and stuff for the family, and realized that was absolutely not the point of time off! So I would take my son to preschool and then keep going. My husband worked until preschool pick-up time, then gave our son lunch and some play time, then put him down for his usual 3-hour nap, and went back to work with the baby monitor next to his desk. If our son woke up, my husband handled it. If he slept, my husband kept working.
My husband learned that I needed to be happy for myself, and for everyone else to be happy. We both understood that, if I waited for everything else to be done, I'd never ever get my own needs met.
So I used my special time to take myself to lunch if I couldn't find a friend (I took a good book or a few crossword puzzles or a dumb magazine), I went to the movies by myself (really fun - no crowds, just sitting in the dark at a flick my husband didn't care to see), I browsed in stores for stuff I wasn't going to buy but wanted to fantasize about, I went to get fitted to a new bra, I got a facial, etc. Very restorative!!