Discipline strengthens the mind so that it becomes impervious to the corroding influence of fear.
Fear comes from uncertainty. When we are absolutely certain whether of our worth or worthlessness we are almost impervious to fear.
It is of course further indication that a fundamentalist right has really taken over much of the Republican Party People might cite George Bush as proof that you can be totally impervious to the effects of Harvard and Yale education.
The most common objection that I hear to walking as exercise is that it's too easy that only sweaty strenuous activity offers real benefits. But there is abundant evidence that regular brisk walking is associated with better health including lower blood pressure better moods and improved cholesterol ratios.