Imagine there is a glass of water on a table in front of you. It has water in it but it is not full. How do you describe the glass? Do you say it is half full or half empty? If you say half full, you might be an optimist. If you say, half empty, you might be the opposite -- a pessimist. Optimism and pessimism represent your general attitude toward certain situations or to life in general. And your attitude about life may be more important to living than you think. A new study suggests that your level of optimism may affect your health. People who are optimistic may live longer than those who are pessimistic. Researchers at Harvard University’s School of Public Health in Boston did the study. They compared women with a general expectation that good things will happen to women who were less optimistic. They found that the optimists had a much lower risk of getting several deadly diseases, including cancer, heart disease, stroke, respiratory disease and certain types of infection.