Mobile health apps are increasingly being recognized as effective tools for improving the efficiency and sustainability of healthcare systems. However, a major challenge faced by the industry is achieving long-term adoption of Apps. This is a critical issue because many apps are abandoned after only a few uses, and low adoption rates limit the potential impact of these apps on healthcare outcomes. In this paper, we examine this issue by integrating the Customer Value Theory and the Person-Artifact-Task model to study how the functional experience of app users, derived from technology features such as perceived ease of use, personalization, and usefulness, enables a state of flow through the users' hedonic and social experiences of recognition and attractiveness. We comprehensively measure the impact of the psychological state of flow in terms of users' cognitive, emotional, and conative responses. Our results indicate that the functional experience of users is central to achieving flow through hedonic and social experiences, while other antecedents of flow, such as health severity and health empowerment, have a lower impact on app use. Developing a positive psychological response towards Apps is also essential to improve users' perception of health improvement, satisfaction, and loyalty. By understanding the factors that contribute to long-term adoption of apps, we can better design and promote these apps to improve healthcare outcomes and promote sustainable healthcare systems.