Physically, I take care of myself by eating healthy (fruits and veggies every day, no junk food), exercise regularly (at least 3 half-hours a week, often more), drink lots of filtered water (1.5-2.0 litres a day), get enough sleep (8 hours a night).
Mentally, I keep my thoughts positive and maintain an optimistic outlook on life.
Emotionally, I deal with my issues methodically and not wait for them to fester.
Spiritually, I take time for myself every day; peace and quiet, meditation, communing with the deity of your understanding, whatever works for you. The important thing is to understand that health is holistic. Just taking care of the physical aspects is not enough. Stress management is all-important.