“How do I practice mental self-care?”

Read books on the matter and the issues you need done. Then try to fit it into your frame of mind

Caring for and not abusing your brain is as important as it is with other parts of you body. Adequate sleep, relaxation, nutrition, and not over-taxing your brain are all parts of self-care. Learning how to better deal with today's stressors also is important, whether that involves meditation, prayer, stopping negative self talk, or other strategies are all important to caring for your mind.

Start with a healthy diet and exercise in addition to good night sleep.

- Focus on your strengths and problem solving, focus on the future not past , focus on your health and not illness .
- Live Healthy, eat healthy foods, get enough sleep, exercise regularly, and avoid drugs and alcohol. Manage stress and go for regular medical check-ups.
Practice good hygiene. Good hygiene is important for social, medical, and psychological reasons in that it not only reduces the risk of illness, but it also improves the way others view you and how you view yourself.
- See friends to build your sense of belonging. Consider joining a support group to make new friends.
- Try to do something you enjoy every day. That might mean dancing, watching a favorite TV show, working in the garden, painting or reading.
- Find ways to relax, like meditation, yoga, getting a massage, taking a bath

Keep your symptoms in check according to your diagnosis. Sleep, balanced diet, exercise, and keep your stress levels low. You should consult your physician as soon as possible when you notice any changes.

See this link for some insight into your question:
https://www.multicare.org/news/self-care-101-for-mental-health-month/

Also, see this link:
https://www.psycom.net/25-best-mental-health-apps