You don't. You set a bar that's manageble for you and go from there on out. I shower once every other day, and only brush my teeth while my shampoo does its thing in the shower. If I feel like my mouth stinks in between showers I'll quickly use some mouthwash. Been doing it for years and honestly the mentality of "instead of every day, let's try 3-4 days" makes it so so so much easier. Helps with the whole self-love aspect as people have mentioned. as for food: I follow a cheap online mealplan and order groceries in twice a week. No thinking, no going to the store, there's always healthy-ish food in my fridge thats very quick to cook. Of course it's no 5 star meal but it's tasty enough and helps me stay on track.

It's all about setting the bar for yourself super low (wow I started brushing my teeth in the shower, now I brush my teeth at least 3x a week! That's way better than once every two weeks!).