An essay excerpted from an 1890's book on psychology. It emphasizes the importance of making your nervous system - your automatic response system - your ally in all of your endeavors. It's a very early predecessor of the System 1 / System 2 split, between a conscious, slow, deliberate mind and a fast, intuitive, subconscious mind.
By doing something a little hard, or a little scary, every few days, you build up capacity in that direction, aligning your automatic responses with the you your reflective self wants you to be. In this vein you should keep an eye on behaviors and promote good habits and avoid bad habits. Seize the opportunity to act on every opportunity in the direction of your Goals and the person you want to be - that's how they become part of the brains action set.
The author urges us to be a little bit heroic every few days so that when the hour of dire need is upon you, you're not unnerved and you are able to do what's right and noble. This reminds me of Stoic teachings.