This literature review presents an overview of an ancient Indian personality system that shows promise for playing an important role in the applied research on well-being and spirituality: the concept of tri-guna. The core proposition of this concept is that the psyche consists of three energies ("gunas") called sattva, rajas and tamas. They are said to be present in everyone in different degrees, explaining differences not only in behavior but also in well-being and spirituality. It is assumed that a dominance of sattva is favorable for well-being. In the first part of this chapter, we provide a summary of indicators for the three gunas, extracted from the available literature, and present empirical findings. The indicators are given separately for cognition, emotion, motivation, social and physical factors, the environment and behavior in general. In the second part we discuss interventions that are claimed to increase sattva and thereby further well-being. This review can be used as a theoretical basis for a more systematic empirical examination of the concept.