Life-style and therapeutic behaviors, namely diet and exercise, are important factors in changing the conditions of patients with diabetes mellitus. In the past, to encourage appropriate therapeutic behavior by patients, therapists instructed them about the disease and the treatments. On the other hand, in recent years, supportive therapy with respect to the problem solving abilities of patients has been introduced. Many effects of such supportive therapy have been reported, but there are still some patients who cannot display their abilities. To support such patients effectively, it is necessary to understand them more comprehensively. In this paper, while showing the process of learning, the authors discuss the significance of understanding patients and the approach to more comprehensively understanding them. Though both the words encouraging patients to adopt better behavior and psychotherapy techniques have gained attention, the authors place emphasis on the importance of the approach in the preparatory stage.