This article illustrates the use of quantitative time-sampling data in developing a psychology of “optimal experience” to help in the psychiatric development of adequate rehabilitation approaches. The Experience-Sampling Method was used on a sample of 47 Italian adolescent students to measure fluctuations in their experience. We found that the ratio of subjectively experienced challenges and skills was a fundamental parameter that predicated optimal experience as well as boredom and anxiety. In contrast, “low” experience in daily life was viewed as a risk factor that could be minimized to increase the quality of life. Monitoring fluctuations in optimal and low experience may therefore be an important tool in developing personalized psychiatric rehabilitation plans.