<p>Research in positive psychology has identified numerous experiences, motivations, and activities associated with well-being. However, effects are often modest, heterogeneous, and difficult to sustain over time, and increases in engagement can sometimes coincide with strain or burnout. These patterns are typically treated as anomalies or methodological limitations. In this paper, we argue that they reflect a deeper theoretical assumption: that well-being accumulates additively from positive experiences. We propose the Dynamic Cost–Recovery Model of Well-Being, a process-level framework that conceptualises well-being as an emergent outcome of dynamic interactions between costs and recovery unfolding over time. The model advances five propositions: that many flourishing-relevant experiences impose structural costs; that recovery is necessary for benefits to accrue; that well-being effects are temporally displaced; that effects are non-additive; and that timing and sequencing moderate outcomes. By integrating insights from Self-Determination Theory, Broaden-and-Build Theory, and the Positive Activity Model, the framework explains why identical experiences can produce divergent well-being trajectories across individuals and occasions. We discuss implications for theory, research design, and intervention development, and outline a research agenda for studying well-being as a dynamic system rather than as the cumulative result of positive experiences.</p>