In this paper, I discuss the systemic features of the life-span development approach which was initially elaborated by Baltes (1989) and more recently considered by Greve (Integrative Psychological and Behavioral Science, 1–21, 2023). I argue that the life-span development approach should recognize the agentivity of people as they not only passively react to changes inside and around themselves but rather imaginatively co-construct their selves (and, their environment) through aging. The irreversibility of human development is highlighted in this paper simultaneously with the recognition of the significance of past phenomenological experiences for self-construction. People are considered as historical agents who evolve through gradual qualitative transformations instead of jumping from one discrete (age) category to another. I consider “migration” as a metaphor for “development” (aging) as both imply movement from one temporal position to another as well as moving from one social position to another. The changes related to aging put an adult in a position similar to immigrants who occur abroad and need to make sense of their new positions in relation to their personal and cultural background and the immediate reality/context they live in. Migration and aging both lead to the innovative mixture of the meaning of old and new experiences/knowledge and the creation of new forms of selfhood and personal understanding at different temporal positions.