This is one of the main three things I'll post about: Exercise, Diet and Play.
It is hard to believe just how dramatically exercise affects academic achievement. The evidence is clear and overwhelming: The single simplest way to boost academic performance is to add vigorous exercise - at any age.
The book "Spark" by Dr. John Ratey gives one of the best overviews available in a very readable and understandable format. And the impact on academics is just the beginning: stress, anxiety, depression, attention deficit, menopause, and aging - all are positively impacted by exercise.
The beauty also is that it does NOT mean you have to become an "athlete" or a "runner". "Walking like you're late" does the trick just as well. Start at your "A" and then find your "B" and work to maintain that. Jumping to "D" is a mistake: raises the potential for injury and, perhaps more importantly, makes it harder to successfully sustain. "I knew I was no good at this!".
And we also have a mistaken notion about energy and exercise. If we feel a bit tired, we tend to think that exercise will make it worse. If all else is going well (healthy diet and enough rest), exercise actually adds to your energy level.
Happy walking or running or swimming or .... whatever!