I cannot too strongly emphasize the importance of walking alone, for then you have shifted your nerve energy from the dry cell battery of the brain to the magneto, which is the spinal cord. The spinal cord works automatically and it doesn't wear itself out. The brain tires if it uses its energy.
In walking you use the thought and the brain impulse to start the magneto then the spinal cord action is automatic.
This automatic action of the spinal cord is a wise provision of nature to conserve strength.
The spinal cord energy is what you might call automatic habit.
For instance, in dressing and undressing yourself you will recall that you put on or take off your clothes in regular order without giving the matter any thought. It is just habit.
If you wish to demonstrate the difference between the control of the physical body by brain impulse and the spinal cord impulse, try this some morning: Start out on your walk, and mentally frame sentences like this as you walk, "right step, left step, right step, left step," and so on; give thought to each step you have taken and notice how tired you will be when you have gone half a mile.
The next morning start to walk, walk naturally, give no thought to walking, keep your mind on the beauties of nature by which you are passing or in pleasant soliloquy and you will feel no fatigue.
There isn't a bit of theory in this chapter; it is positive practical sense I have proved by my own experiences and by the experiences of everyone to whom I have made this suggestion of walking alone.
The moral is this—walk every morning and walk ALONE.