Care about how you are today because you will be so much better tomorrow.

You charge your phone every night without asking whether it has earned the electricity. It is low-grade maintenance, done automatically, for an object, on the reasonable grounds that it has to work tomorrow.

Care for yourself on a hard day is about that unremarkable. Water. Something eaten before three o'clock. Being horizontal by midnight.

None of it is treating yourself and none of it requires believing anything. Tomorrow needs somebody to arrive in reasonable condition, and you are the only one available for the job.