Whenever the immune system deals successfully with an infection, it emerges from the experience stronger and better able to confront similar threats in the future. Our immune system develops in combat. If, at the first sign of infection, you always jump in with antibiotics, you do not give the immune system a chance to grow stronger.

Alternative models are neither right nor wrong, just more or less useful in allowing us to operate in the world and discover more and better options for solving problems.

Meditation while walking has a long, noble history in ancient spiritual disciplines.

Improper breathing is a common cause of ill health. If I had to limit my advice on healthier living to just one tip, it would be simply to learn how to breathe correctly. There is no single more powerful -or more simple- daily practice to further your health and well being than breathwork.

If you have difficulty sleeping or are not getting enough sleep or sleep of good quality, you need to learn the basics of sleep hygiene, make appropriate changes, and possibly consult a sleep expert.

To be clear, I worry as much about the impact of the Internet as anyone else. I worry about shortening attention spans, the physical cost of sedentary "surfing" and the potential for coarsening discourse as millions of web pages compete for attention by appealing to our base instincts.

Shorter daylight hours can affect sleep, productivity and state of mind. Light therapy, also known as phototherapy, may help. It uses light boxes emitting full-spectrum light to simulate sunlight.