Merriam-Webster defines health as "the general condition of the body" and "the condition of being sound in body, mind or spirit," especially "freedom from physical disease or pain." By this definition, one who is healthy is not simply free from disease or pain, but also has a realistic (and preferably positive) outlook on life, is able to build stable and enjoyable relationships with other people, and has the physical ability to not only achieve the tasks and responsibilities of daily life but also to enjoy recreational activities.
Taking care of one's physical, mental and emotional health is a priority for many, but unfortunately it is a priority that sometimes falls by the wayside or takes a second seat to economic difficulty, lack of time, or other factors. However, taking care of one's health in the long run saves time, money and stress (consider the proverb of the apple a day). Taking care of one's physical health involves knowledge of the human body and its processes. The elements of physical health include nutrition, exercise, rest (sleep), cleanliness (environmental and personal hygiene) and regular medical and dental care.
Mental health and emotional health are closely tied to physical health; our mental state literally changes the physiology of the body. The elements of mental health include emotional health and development, social relationships, and handling stress. Proper nutrition and exercise may seem like obvious ways to take care of your physical health, but handling stress is also critical to maintaining physical well-being. Stress can damage mental health and emotional health, and contributes to a host of physical problems including ulcers, migraine headaches, rashes and hair loss. There are many methods for handling stress--relaxation, meditation, exercise--and the key is to find the method that works for you and to recognize the importance of practicing that method.
There is more information now than ever on what constitutes proper nutrition, exercise, and even emotional development--and much of it is contradictory. It may seem impossible to sort through this information, so soliciting the advice of a medical professional is wise. Although it requires effort and discipline, a healthy lifestyle can provide a sense of well-being that is entirely worth it.