To live a long and healthy life, we need to understand what constitutes "good health" in the first place. Although the term will differ slightly from one person to the next, in 1948, the World Health Organization created a general definition of good health still used by healthcare providers today:
"Health is a state of complete physical, mental, and social well-being and not merely the absence of disease and infirmity. A resource for everyday life, not the objective of living. Health is a positive concept emphasising social and personal resources, as well as physical capacities".
Good health sounds quite complicated by their definition, so it's worth breaking down some of the critical points. Good health isn't merely about being free of disease and disorder. Of course, these are the primary goals, but what the WHO emphasises is the need for balance in all aspects of life.