The goals of this pilot study are to empirically test different interventional approaches to induce positive affect and self-affirmation. At the start of the study all patients in conjunction with their physicians will select a program of mild to moderate physical activity or exercise to be adopted and maintained on a routine basis. Patients also will complete the Paffenbarger Physical Activity and Exercise Index. Patients then will be divided into four groups according to the intervention they receive: 1) positive affect; 2) self-affirmation; 3) positive affect and self-affirmation; 4) control. The main outcome is the change in the Paffenbarger Physical Activity and Exercise Index scores from enrollment to 4 weeks.