Maintaining a daily positive affect – engaging in a mild, happy self-affirming attitude – helps people with chronic diseases  to make better decisions about their health. Mary E. Charlson, from Weill Cornell Medical College (New York, USA), and colleagues completed three studies involving 756 patients in randomized controlled trials that show that people can use positive affect and self-affirmation to help them make and sustain behavior change.  The same intervention was used in all three studies. Patients were encouraged to think of small things in their lives that make them feel good (such as seeing a beautiful sunset) when they get up in the morning and throughout their day. Patients were also asked to use self-affirmation to help them overcome obstacles to their plan by recalling moments in their lives they are proud of, such as a major personal accomplishment.  The behavior changes employed in the studies are known to be beneficial – ranging from increased physical activity for coronary artery disease to a managed medication regimen for high blood pressure or asthma. Subjects were randomly assigned either to the experimental "positive affect" group or to a control group. Both groups made personal contracts to adhere to their behavior plans, were given an educational guide on the importance of their intervention, and received phone calls every two months to check in on their progress. Along with daily use of positive affect, patients in the experimental group received surprise gifts prior to the phone sessions. Results were measured at the completion of the yearlong studies. For coronary artery disease, 55% of patients practicing the positive affect/self-affirmations increased their physical activity, as compared with 37% in the control group; the positive affect group walked an average of 3.4 miles a week more than the control group. For high blood pressure, 42% of the positive affirmation group adhered to their medication plan, as compared with 36% in the control group. For asthma patients, there was no difference in energy expenditure between the two groups; however, there was some benefit for patients requiring medical care during the trial.