In Zen, “spiritual self-care” is an oxymoron.
A fundamental teaching of Buddhism is the concept of no-self. When the Buddha looked into the Nature of Everything he saw nothing there that was him. He realized that the perception that we are separate from each other and everything else is the primary source of our suffering.
In Zen, spiritual self-care is recognizing the nature of suffering and a way through. The practice involves focusing your attention and observing the nature of your mind. The hard part about observing your mind is that you do it with your mind. Your mind creates all kinds of distractions that suck you in and set your focus wandering. That is the nature of mind. That is what you observe as you practice bringing your attention back to your point of focus.
The ultimate point of focus is the present moment. The present moment is where you live. As long as you are alive, you have your breath. When you focus your attention on your breath, it is grounded in your body in the present moment. Doing that, with a compassionate attitude, recognizing that there is suffering and seeking a way to ease that suffering is the basis of spiritual self-care. It is not so much the self taking care of the spirit, but the spirit taking care of the self.
Spiritual self-care involves taking care of your body and mind with a spiritual sense of caring. It involves eating well, sleeping enough, getting exercise, bathing, and brushing your teeth. It involves connecting with others, practicing compassion toward them and opening yourself to their compassion. It involves slowing down and being present right where you are with things just as they are, even if it hurts. When things hurt, be present with the pain and practice compassion for yourself. See what could be wrong and do what you can to help yourself feel better.
Two reliable ways to practice spiritual self-care and help yourself feel better are practicing generosity and gratitude. Those practices help us abide in our interconnected nature, which tends to feel good.