(ט) רַ֡ק הִשָּׁ֣מֶר לְךָ֩ וּשְׁמֹ֨ר נַפְשְׁךָ֜ מְאֹ֗ד פֶּן־תִּשְׁכַּ֨ח אֶת־הַדְּבָרִ֜ים אֲשֶׁר־רָא֣וּ עֵינֶ֗יךָ וּפֶן־יָס֙וּרוּ֙ מִלְּבָ֣בְךָ֔ כֹּ֖ל יְמֵ֣י חַיֶּ֑יךָ וְהוֹדַעְתָּ֥ם לְבָנֶ֖יךָ וְלִבְנֵ֥י בָנֶֽיךָ׃
(9) But take utmost care and watch yourselves scrupulously, so that you do not forget the things that you saw with your own eyes and so that they do not fade from your mind as long as you live. And make them known to your children and to your children’s children:
(ה) הַמְכַבֶּה אֶת הַנֵּר מִפְּנֵי שֶׁהוּא מִתְיָרֵא מִפְּנֵי גוֹיִם, מִפְּנֵי לִסְטִים, מִפְּנֵי רוּחַ רָעָה, וְאִם בִּשְׁבִיל הַחוֹלֶה שֶׁיִּישַׁן, פָּטוּר. כְּחָס עַל הַנֵּר, כְּחָס עַל הַשֶּׁמֶן, כְּחָס עַל הַפְּתִילָה, חַיָּב...
(5) One who extinguishes the lamp on Shabbat because he is afraid due to gentiles, from whom he is hiding in his home, and due to thieves, or if one is afraid due to an evil spirit, or due to the sick person so that he will sleep, he is exempt. However, in a case where he extinguishes the flame in order to spare the lamp, spare the oil, or spare the wick, he is liable.....
..“The Evil Spirit is referring to melancholy. There is a type of melancholy that will cause the ill person to lose his mind when he sees light or when he is amongst other people. He finds peace only in darkness, in solitude, and in desolate places.”.
דְּאָגָה בְלֶב אִישׁ יַשְׁחֶנָּה רַבִּי אַמֵּי וְרַבִּי אַסִּי חַד אָמַר יַשִּׂחֶנָּה מִדַּעְתּוֹ וְחַד אָמַר יְשִׂיחֶנָּה לַאֲחֵרִים
(Maimonides' Regimen of Health, a treatise on hygiene,was written in 1198 for the Egyptian sultan Afdal Nur al-Din Ali, who suffered from attacks of depression accompanied by physical symptoms)
If emotional stress is maintained for a long period, one will definitely become ill.
Constant anxiety damages the body.
Emotional experiences produce distinct changes in the body… Emotions also have an effect on the circulation of the blood and the functioning of one’s organs…They affect the body and they in turn are affected by the constitution of the body.
The physician should think that every sick person has a constricted heart while every healthy person has a broad state of consciousness. Therefore the physician should remove [from the patient] all emotional activities that lead to anxiety. This way the health of the patient is preserved. This principle takes precedence in the cure of any patient, especially if his illness is specific to this area like depression…
The physicians have instructed that one must pay attention and constantly consider ones emotional activities. Maintaining them in equilibrium, during health and illness, must take precedence over any other regimen.
“The physician should not think that medical knowledge (alone) can set aside emotional instabilities. Psychology and ethical philosophy are necessary…
Contemplation alone reduces bad thoughts, anxiety and distress. Most thoughts that cause distress, sorrow, sadness or grief, occurs from one of two things:
1. Either one thinks of the past like the loss of money or a beloved one
2. Or one thinks of something that may occur in the future like a possible loss or injury and one fears their coming.
Yet it is known through rational observation that thinking about the past is of no benefit at all. Sorrow and grief over the past are activities of those who lack the influence of the intellect. There is no difference between a person who grieves over lost money and the like, and someone who grieves because he is human and not an angel, or a star, or similar thoughts which are impossibilities.
Similarly, any anxiety that results from thoughts about what may happen in the future are pointless because every possible thing lies in the realm of possibility: maybe it will happen and maybe it will not. Let a person replace anxiety with hope [in G-d] and with this hope it is possible that in fact the opposite of what one fears will actually happen, because both what one fears and its opposite are (equally) in the realm of possibility.”
The following is from Rambam's (Maimonides) introduction to Pirkei Avot (Ethics of the Fathers).
(ב) והמשל בו שישים הכוונה באכילתו, ושתייתו, ומשגלו, ושנתו ויקיצתו, ותנועתו, ומנוחתו בבריאות גופו לבד, והכוונה בבריאות גופו שתמצא הנפש כליה בריאים שלמים לקנות בחכמות וקנות מעלות המדות (ומעלות) השכליות עד שיגיע לתכלית ההיא. ועל זה ההקש לא תהיה אז כוונתו אל ההנאה לבד עד שיבחר מן המזון והמשתה הערב וכן בשאר ההנהגה, אבל יכוין אל המועיל, וכשיזדמן שיהיה ערב יהיה, וכשיזדמן שיהיה בלתי ערב יהיה, או יכוין אל הערב על דרך חכמת הרפואות כמי שחלשה תאותתו למאכל ויעירהו במזונות המתובלות הערבות, שנפש האדם מתאוה להם, וכן אם תתעורר עליו לחה שחורה יסירה בשמיעת הניגונים ובמיני זמר, והטיול בגנות והבנינים הנאים, וחברת הצורות היפות וכיוצא בזה ממה שירחיב הנפש ויסור המרה השחורה ממנה, והכוונה בכל זה שיבריא גופו, ותכלית הכוונה בבריאות גופו לקנות חכמה, וכן כשיתעסק בקנות הממון יהיה תכלית כוונתו בקבוצו שיוציאהו במעלות, ושימצאהו לחושי גופו ולהמשיך מציאותו עד שישיג וידע מהש"י מה שאפשר לדעתו:
(2) So, his only design in eating, drinking, cohabiting, sleeping, waking, moving about, and resting should be the preservation of bodily health, while, in turn, the reason for the latter is that the soul and its agencies may be in sound and perfect condition, so that he may readily acquire wisdom, and gain moral and intellectual virtues, all to the end that man may reach the highest goal of his endeavors. Accordingly, man will not direct his attention merely to obtain bodily enjoyment, choosing of food and drink and the other things of life only the agreeable, but he will seek out the most useful, being indifferent whether it be agreeable or not. There are, indeed, times when the agreeable may be used from a curative point of view, as, for instance, when one suffers from loss of appetite, it may be stirred up by highly seasoned delicacies and agreeable, palatable food. Similarly, one who suffers from melancholia may rid himself of it by listening to singing and all kinds of instrumental music, by strolling through beautiful gardens and splendid buildings, by gazing upon beautiful pictures, and other things that enliven the mind, and dissipate gloomy moods. The purpose of all this is to restore the healthful condition of the body, but the real object in maintaining the body in good health is to acquire wisdom. Likewise, in the pursuit of wealth, the main design in its acquisition should be to expend it for noble purposes, and to employ it for the maintenance of the body and the preservation of life, so that its owner may obtain a knowledge of God, in so far as that is vouchsafed unto man.