The greatest accomplishment of the 20th century--the doubling of the human lifespan--has brought issues related to brain health to the forefront of public health policy. Given that our bodies are outlasting our minds, maximizing brain health is the scientific cause of this millennium. In this paper, we address three major issues related to maintaining and, perhaps, enhancing brain health in seniors. First, we define the construct of brain health fitness. Second, we discuss gist reasoning as a metric of brain health fitness and as a construct of brain health training. Lastly, we propose that healthy brain habits can be practiced by incorporating gist reasoning during complex everyday life and leisure activities to elevate chances for maintaining brain health fitness beyond retirement for a sustainable future. (Contains 1 table.)