EXERCISERegular aerobic exercise and a healthy diet are probably the two most powerful ways of improving your physical and mental health. Of course the mind and body are really an interconnected system. Recent scientific research has clarified how physical exercise can help someone feel better emotionally and also more surprisingly can also improve cognitive functioning.
Research shows that people who have exercised regularly are less likely to develop Alzheimer's disease. If they do develop Alzheimer's, it progresses more slowly. Most people experience some cognitive decline as they age, and that doesn't happen as much for people who exercise regularly.
Some research studies have shown that physical exercise can improve or even "cure" Major depression. In the short run, exercise certainly helps people with either depressive or anxieties disorders to feel better for the moment even if it does not produce lasting cure. Another fringe benefit is that many patients with either anxiety or depressive disorders become socially isolated which makes things worse. By choosing to exercise in a group situation, for example an aerobics class, the benefits of socialization also occur.
Another way that physical exercise can help improve a serious depression is that it helps a depressed person become more active. Commonly depressed people have very low energy and they find it very difficult to initiate activities. They also believe that they should wait until they stop being depressed and then it will be easy to become active again. Research shows that the opposite is more effective. In other words it's important to become more active first. As a result of that the depression will decrease.
Other forms of physical activity may also be beneficial but in different ways. Yoga, for example, tends to restore a better balance of the autonomic nervous system. Very depressed or anxious people have too much activity of their sympathetic nervous system, which is related to the "fight or flight" response. Serenity and relaxation are associated with parasympathetic activity which increases from yoga. For more details, please see my discussion about meditation and yoga.
Even if you have a physical disability, you may be able to find ways to increase your physical activity without hurting yourself. You could try taking deep breaths while you simultaneously raised both arms over your head. Water aerobics is easier on the joints. Use your creativity. Find some way to do an experiment with your own body for about three months and see what happens.