Make light of your feelings. Never mind them. It is no disgrace to FEEL like a coward. It is a purely physical thing; due to nervous depletion. But it is a disgrace to ACT like a coward. In other words, ACT at all times like the well, healthy, poised person that you want to be.
This does not mean that when you are fagged out physically, you are to keep right on working as if you were a laboring man just starting out for a day in the harvest field.
When you are physically tired, see that you rest your body. See that you do no more mental work than you can do with pleasure, and without depleting your physical energy. You will have to regulate your hours of mental labor and keep them regulated with a strict hand.
Live a life of alternate mental expression and physical expression. Sir Walter Scott used to walk one hour for every hour that he spent at his literary work. This is a very good rule, but in these days we think we cannot take so much time for the physical.
So, we have to condense our physical exercises. When you have worked two or three hours at mental work, see that you go out for a walk for a half-hour or an hour, or go for a game of golf, or better still a game of tennis, or a few miles run on a bicycle or half an hour’s horseback riding, etc. If you cannot do this, take five or ten minutes’ brisk physical culture exercises, with more full breathings and affirmations; follow this with a few minutes of absolute rest and relaxation, lying flat on your back without a pillow. Then you will find yourself ready to get up and do another hour or two of mental work.
Break every day into sections like this.
When you work with your mind it is as if your mental energy went out at the top of your head.
When you work with your body it goes down through your body rejuvenating, regenerating cleansing as it goes. When you sleep and when you relax, energy flows into you. When you make any sort of effort, physical or mental, energy is pressed out of you— expressed. These activities are a parallel of the breathing exercises— every exhalation must be followed by an equal inhalation, or the fatigue poisons overcome you. Breathing exercises are equivalent to forcing the draft and burning up the fatigue poisons.
William Towne | The Nautilus, 1912