How might managing one's own physical health affect the stability of social systems beyond the individual's life?

Physical health seems likely to lead to two effects.

1. More cognitive resources available for decision-making. When you become healthier, you first gain some slack. Of course, if exercise has overactivated the sympathetic nervous system, one could say cognitive resources are reduced in that state, but if health improves overall, it should be positive for managing chronic stress, and resources should free up as well. The more an individual's resources grow, the higher the probability of making rational decisions, and the stability of society as a whole will also increase.
2. Restoration of self-efficacy. I have an earlier post that voiced concern about 'successfully performing tasks that are achievable,' but I think the positive effect is greater for people in situations where self-efficacy is weak and anxiety and depression are high. This is because the anxiety you feel right now has to be relieved before there is room to take a rational approach to acceptance. Therefore, through these two main pathways, managing health will also raise the stability of society itself.