Self care gives you choices.
I like to be able to choose things. For instance, I like to be able to choose between chicken nuggets or a salad for lunch (or if you're in Pittsburgh, you put nuggets and fries and shredded cheese and ranch on that salad, but that's a whole separate issue!) I like to be able to decide what I want to work on. I like to decide what activities I do in my free time. I like to be able to decide what goals best fit my vision for the future.
I like to think about self care as practices that help me have choices. Because when I am run down, or burnt out, or just trying to survive, I have much fewer options. For example:
I pass out on the couch when I didn't mean to
I take 2 hour naps randomly in the middle of the day when I don't have time to
Everything is due tomorrow so I have no choice about what I work on
I don't have the option to do activities that recharge me because I have so much work that is due now, or soon
I have less options for my food because I don't have time to prep my own meals, or my choices are limited
When I thought about self care as bubble baths and shopping trips and things that I did because I deserved them after a period of work, I swung wildly from overindulgence to austerity. I could never get the balance right if my self care was only reactive; if I had to earn self care by working, then I either held out until I reached a stopping point, or I cared for myself "early" and felt guilty about it.
But I am now trying to think of my self care as something that is proactive: I take care of myself in the present so that in the future, I have choices.
I prioritize sleep, trying to get at least 7 hours a night, so that my chronic illness doesn't have another reason to flare (it does that all on it's own!) I also do this to manage my fatigue during the day, so when I sit down to work, my brain cooperates.
I try to work in small, sustainable ways so that no one day of work leaves me so exhausted that I have to recover for multiple days afterwards.
I work really hard to have an awareness of who needs what from me when, so that deadlines don't sneak up on me and I can best use the limited resources of time and energy in a conscious way.
I try to meal prep so that I have choices in the fridge that make my body feel good, and that I save money by avoiding last minute hangry takeout ordering.
I schedule time with friends and family members so that even if my work isn't "done" I can still be with people who care about me, and who recharge me. Bonus points on this one because if you make the plans, you can have more influence on the time!
It can be hard to break long standing habits of overwork, especially when so much of academic culture is not only overworking yourself, but performing that misery as a sign of your dedication. It was easier for me to "take time" to take care of myself if I viewed it as a future investment. By taking care of myself now, I give myself choices later. And choices help me feel like this is a life that I am living on purpose, not just one that I'm reacting to, crisis by crisis.