<p>Contemporary approaches examining the determinants of happiness have posited that happiness is determined bidirectionally by both top-down, global life satisfaction and bottom-up, domain satisfaction processes. We propose a personalized happiness perspective, suggesting that the determinants and consequences of happiness are idiographic (that is, specific) to each individual rather than assumed to be the same for all. We showed the utility of a personalized happiness approach by testing associations between life and domain satisfaction at both the population and personalized levels using nationally representative data of 40,074 German, British, Swiss, Dutch and Australian participants tracked for up to 33 years. The majority of participants (41.4–50.8%) showed primarily unidirectional associations between domain satisfactions and life satisfaction, and only 19.3–25.9% of participants showed primarily bidirectional associations. Moreover, the population models differed from personalized models, suggesting that aggregated, population-level research fails to capture individual differences in personalized happiness, showing the importance of a personalized happiness approach. Patterns of individual differences are robust, yet distinguishing between individual-level patterns and random error is challenging, highlighting the need for future work and innovative approaches to study personalized happiness.</p>