Is your glass half-empty or half-full? How you answer this age-old question about positive thinking may reflect your outlook on life, your attitude toward yourself, and whether you're optimistic or pessimistic.

In fact, some studies show that these personality traits — optimism and pessimism — can affect many areas of your health and well-being. Positive thinking also is a key part of effective stress management. Positive thinking doesn't mean that you keep your head in the sand and ignore life's less pleasant situations. It just means that you approach the unpleasantness in a more positive and productive way.