This article presents a comprehensive account of the authors' Motivational Theory of Life-Span Development, which integrates the Model of Optimization in Primary and Secondary Control and the Action-Phase Model of Developmental Regulation. The theory focuses on how individuals regulate their motivation to optimize development across major life changes. Key aspects include: 1. **General Challenges and Questions**: The authors identify criteria for adaptive development, such as physiological functioning, cognitive performance, and achievement in various domains. They emphasize the importance of individual agency and the role of developmental goals in shaping life course development. 2. **Individual Agency and Developmental Goals**: Individuals are active agents in their own development, striving for goals that reflect developmental tasks and life-course transitions. These goals are directed at specific developmental processes or life-course attainments and are typically intermediate in level of aggregation. 3. **Changing Opportunities and Constraints**: Individuals must adjust to and cope with changing opportunities and constraints throughout their lives. Biological and societal factors create a trajectory of increasing and decreasing control capacity, with critical transitions and sequential constraints. 4. **Selectivity and Compensation**: Two fundamental regulatory challenges are selectivity of resource investment and compensation of failure and loss. Selectivity involves prioritizing goals, while compensation helps individuals deal with setbacks and maintain motivation. 5. **The Motivational Theory of Life-Span Development**: The theory proposes that primary control capacity is the key criterion for adaptive development. It integrates the original life-span theory of control with the Model of Optimization in Primary and Secondary Control and the Action-Phase Model of Developmental Regulation. The theory emphasizes the importance of goal selection, engagement, and disengagement, and the role of control strategies in these processes. 6. **Life-Span Trajectories of Primary and Secondary Control**: Individuals strive for primary control across different domains and age stages, with trajectories that vary in opportunity and constraint. Secondary control strategies support primary control by adjusting expectations and attributions. 7. **Action-Phase Model of Developmental Regulation**: This model describes the sequential structure of goal engagement and disengagement, including phases such as goal choice, goal engagement, urgent goal engagement, and goal disengagement. It highlights the importance of congruence between changes in opportunities and phases of goal engagement and disengagement. The authors conclude by identifying areas for further empirical inquiry to enhance the theory's conceptual reach.This article presents a comprehensive account of the authors' Motivational Theory of Life-Span Development, which integrates the Model of Optimization in Primary and Secondary Control and the Action-Phase Model of Developmental Regulation. The theory focuses on how individuals regulate their motivation to optimize development across major life changes. Key aspects include: 1. **General Challenges and Questions**: The authors identify criteria for adaptive development, such as physiological functioning, cognitive performance, and achievement in various domains. They emphasize the importance of individual agency and the role of developmental goals in shaping life course development. 2. **Individual Agency and Developmental Goals**: Individuals are active agents in their own development, striving for goals that reflect developmental tasks and life-course transitions. These goals are directed at specific developmental processes or life-course attainments and are typically intermediate in level of aggregation. 3. **Changing Opportunities and Constraints**: Individuals must adjust to and cope with changing opportunities and constraints throughout their lives. Biological and societal factors create a trajectory of increasing and decreasing control capacity, with critical transitions and sequential constraints. 4. **Selectivity and Compensation**: Two fundamental regulatory challenges are selectivity of resource investment and compensation of failure and loss. Selectivity involves prioritizing goals, while compensation helps individuals deal with setbacks and maintain motivation. 5. **The Motivational Theory of Life-Span Development**: The theory proposes that primary control capacity is the key criterion for adaptive development. It integrates the original life-span theory of control with the Model of Optimization in Primary and Secondary Control and the Action-Phase Model of Developmental Regulation. The theory emphasizes the importance of goal selection, engagement, and disengagement, and the role of control strategies in these processes. 6. **Life-Span Trajectories of Primary and Secondary Control**: Individuals strive for primary control across different domains and age stages, with trajectories that vary in opportunity and constraint. Secondary control strategies support primary control by adjusting expectations and attributions. 7. **Action-Phase Model of Developmental Regulation**: This model describes the sequential structure of goal engagement and disengagement, including phases such as goal choice, goal engagement, urgent goal engagement, and goal disengagement. It highlights the importance of congruence between changes in opportunities and phases of goal engagement and disengagement. The authors conclude by identifying areas for further empirical inquiry to enhance the theory's conceptual reach.