Now we're getting to what I believe to be the most important of the six essentials for life. What you think has a greater impact on your health than the other five (what you eat, what you drink, how you exercise, how you rest, what you breathe) combined.

Thoughts, or memories of thoughts, run through your head 24 hours a day, seven days a week -- even when you sleep. You can't get away from thoughts, and thoughts affect your physiology all of the time. Man's level of thought is what separates him from other species. I've learned over the years, with thousands of patients, that thoughts can be creative or destructive, helpful or harmful.

The impact of thoughts on physiology can be demonstrated by this simple example.

Think of a lemon. See yourself slicing that lemon in half. Now, imagine picking up one half and squeezing the juice into your open mouth. If you do this with your eyes closed and really concentrate, you can, and probably will, begin to salivate. Salivation is your body's natural response to neutralize the acid of the lemon. Just the mere thought of pure lemon juice in your mouth can change your body's physiology. Thoughts, it seems, really are things.

Recent studies continue to affirm the link between feelings and one's state of health. For example, feeling helpless may slow the immune system and lower the body's resistance. When under stress, believing that you must be in control can also have an affect on your immunity. Feeling like you should just give up to the stresses of your life may raise your risk of cancer or sudden death. Extreme negative emotions like hostility, cynicism, and distrust may play a part in your risk of heart disease.

Emotions, thoughts, beliefs, and attitudes are not just in your mind, but are directly linked to your overall health through electrochemical occurrences within your body -- physiological responses. Roger Guillemin and Andrew Schally received the Nobel Prize in 1977 for demonstrating that the brain uses chemical messengers to communicate with the body.

You usually know when you're stressed in a negative way. You feel tense or irritable. When you're suddenly frightened or startled, you can feel your body react, like when strange noises go bump in the night, or you have to speak in front of an audience, or another car comes hurtling toward you on your side of the road. Danger rampages and you are stressed. These are modern-day equivalents of the stresses our ancestors felt when they encountered a bear in their cave.

The problem arises because thoughts and emotions you create in your conscious mind also produce chemicals and the body responds to the chemicals, without thought, in order to survive. You fear losing your job and your body produces chemicals, which change bodily functions. The body does this in order to protect itself. As long as the chemicals are being produced, the body is going to respond to them.

When fear is a result of a life-threatening physical situation, the response of chemical production is perfect and ends when the threat ends. But when the situation is not life-threatening -- for example, a worry about something that might happen -- then the same perfect response is performed at an inappropriate time, and it keeps on performing.

If you fear over and over, you eventually live in a state of fear. Your body constantly produces the chemicals necessary to deal with your fears and responds physically to those chemicals. This continual drain of energy to fight or run exhausts your body, which manifests itself in your health. It may lead to illness, disease, pain, a bad cold, the flu, or depression.

Continually exhausting your power to fight puts you on the road to poor health. Fear and other strong negative emotions are major contributors to exhausting your body.

In summary, it seems that negative feelings are associated with the production of disease. If that is so, then the opposite postulate would be that positive feelings produce health. Proverbs 16:24 says, "Pleasant words are as an honeycomb, sweet to the soul, and health to the bones." Feeding the physical body positive thoughts from the conscious mind leads to health.

The beautiful part about all of this is that you can change your current physical condition. If you don't like your physical health or body today, you can take charge and change it. Making changes in the choices you make in the six essentials for life (those choices that led you to your current state of health) will literally change our physical condition -- for better or for worse.