Growing into old age is a personal privilege and a societal achievement. However, it is also a challenge for both the individuals and societies. The impressive gains in extending average physical longevity to 75 years and beyond is not necessary accompanied by high-levels of physical, psychological, and brain “fitness”. Thus, it is important to seek ways to help older adults maintaining functions in these domains in order to maintain life quality in old age. Adaptive assistive devices and environments are promising technological advancements for promoting successful aging. Sufficient plasticity in the aging psychological and neurocognitive systems are necessary for technologies to engender desired effects. Designs and evaluations of assistive technologies need to consider dynamic changes in developmental resources across the lifespan. This paper reviews evidence of behavioral and neurocognitive plasticity in old age and highlights psychological principles for successful aging technologies.