The bottom line is that the human body is complex and subtle, and oversimplifying - as common sense sometimes impels us to do - can be hazardous to your health.

The more people have, the less content they seem to be. In America, the cultural expectation that we're to be happy all the time and our children are to be happy all the time is toxic, and I think that really gets in the way of emotional well-being.

Many exercise forms - aerobic, yoga, weights, walking and more - have been shown to benefit mood.

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.

Happiness is a skill. It requires effort and time.

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.

The underlying idea is that you can prevent disease by balancing your body's pH... None of these claims are true. Furthermore, your body needs absolutely no help in adjusting its pH. Normally, the pH of blood and most body fluids is near seven, which is close to neutral. This is under very tight biological control because all of the chemical reactions that maintain life depend on it. Unless you have serious respiratory or kidney problems, body pH will remain in balance no matter what you eat or drink.