Humans regularly go to the dentist, get their shots, work out at the gym, and take their vitamins. This is all to maintain physical health. Humans also go dancing, take up hobbies, tie one on now and then, surround themselves with music, and, especially on the West Coast, go for therapy. This is all for mental health. In the spiritual realm there is worship at church, meditation, and... not much else. The reason for this is that the spiritual side of man doesn't manifest in the same way physical and mental problems do. Does one ever die of a sick spirit? Is one hospitalized because the spirit is sick? There seems to be no repercussions to neglecting the spirit. Those who attend church regularly fare no better than those who don't, and the benefits of meditation cannot be measured. So, why bother?
Where the spiritual side of man does not demand care and attention, it is the one aspect of a human life that remains after death. What occurs during an incarnation either strengthens or diminishes the spirit, and this sum total forms the basis for the next incarnation. That's why one should bother.
What is spiritual health? As with the human intellect, the spirit grows best when exposed to breadth. Watch the sunset and contemplate the vastness of the Universe rather then crack another beer and stare at the TV. Look with wonder at the variety of human forms and personalities rather than close this out as an intrusion on the status quo. Take responsibility for a small task that improves the life of the least among you, and get hooked on how much better this makes you feel about yourself than if you had spent that bit of time fussing over yourself.