The brain is the citadel of the being. Wrong physical habits affect the brain and prevent the attainment of that which the students desire—a good mental discipline. Unless the youth are versed in the science of how to care for the body as well as for the mind, they will not be successful students. Study is not the principal cause of breakdown of the mental powers. The main cause is improper diet, irregular meals, a lack of physical exercise, and careless inattention in other respects to the laws of health. When we do all that we can to preserve the health, then we can ask God in faith to bless our efforts. CT 299.2
Before students talk of their attainments in the so-called “higher education,” let them learn to eat and drink to the glory of God and to exercise brain, bone, and muscle in such a way as to fit them for the highest service. A student may devote all his powers to acquiring knowledge, but as he disobeys the laws that govern his being he will weaken his efficiency. By cherishing wrong habits, he loses the power of self-appreciation, and he loses self-control. He cannot reason correctly about matters that concern him most deeply, and becomes reckless and irrational in his treatment of mind and body. CT 299.3
The obligation resting upon us to keep the body in health is an individual responsibility. The Lord requires each one to work out his salvation day by day. He bids us reason from cause to effect, to remember that we are His property, and to unite with Him in keeping the body pure and healthy, and the whole being sanctified to Him. CT 300.1
The youth should be taught that they are not at liberty to do as they please with their lives. God will not hold guiltless those who treat lightly His precious gifts. Men should realize that the greater their endowment of strength, of talent, of means, or of opportunities, the more heavily should the burden of God's work rest upon them, and the more they should do for Him. The youth who are trained to believe that life is a sacred trust will hesitate to plunge into the vortex of dissipation and crime that swallows up so many promising young men of this age. CT 300.2
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The teacher whose physical powers are already enfeebled by disease or overwork should pay especial attention to the laws of health. He should take time for recreation. When a teacher sees that his health is not sufficient to stand the pressure of heavy study, he should heed the admonition of nature and lighten the load. He should not take upon himself responsibilities outside of his schoolwork which will so tax him physically and mentally that his nervous system will be unbalanced, for by this course he will be unfitted to deal with minds and cannot do justice either to himself or to his students. CT 300.3
Sometimes the teacher carries into the schoolroom the shadow of darkness that has been gathering on his soul. He has been overtaxed and is nervous, or dyspepsia has colored everything a gloomy hue. He enters the schoolroom with quivering nerves and irritated stomach. Nothing seems to be done to please him; he thinks that his pupils are bent on showing him disrespect; and his sharp criticisms and censure are given on the right hand and on the left. Perhaps one or more of the students commits errors or is unruly. The case is exaggerated in his mind, and he is severe and cutting in his reproof of the one whom he thinks at fault. And the same injustice afterward prevents him from admitting that he has taken a wrong course. To maintain the dignity of his position, he has lost a golden opportunity to manifest the spirit of Christ, perhaps to gain a soul for heaven. CT 301.1
It is the duty of each teacher to do all in his power to present his body to Christ a living sacrifice, physically perfect, as well as morally free from defilement, that Christ may make him a co-worker with Himself in the salvation of souls. CT 301.2