We're only part way through this, Dr. Sanjay Gupta writes. If we stop now, it may not just be back to square one. We may be worse off than we started.

For a moment, think of the United States as a human body. Full of heart and mind. Bile and blood. Muscle and fat. Like any body, it has its strengths and weaknesses, and must consistently work to prevent disease and optimize function. It needs to nourish itself, exercise, and take care of its physical and mental health.