Musar su Genesi 49:15

Experience also taught us in past days when the plague was rife, may the Merciful One save us, that whoever submitted to the burden of the doctors’ orders¹⁵Literally: bowed his shoulder to bear [the weight of] the doctors’ instructions. Compare Genesis 49:15. vis-à-vis diet, etc., wisely, not foolishly, was not affected by plague or disease, may the Merciful One save us. Thus, since all religious behavior is altered, according to halakhah itself,¹⁶R. Salanter is saying that one should not view the shift away from mourning and grief as the interference of a “secular” or “outside” approach in halakhic practice. Rather, halakhah itself commands us to follow the instructions of physicians. This is in keeping with R. Salanter’s leadership during the cholera epidemic in Vilna in 1848. R. Salanter insisted not only on doing life-saving work on Shabbat (and eating on Yom Kippur to protect life), but that all should follow doctors’ orders and do anything that promotes health, without trying to minimize medically prescribed halakhic changes or seeking exemptions for religious activities. at this time, one should not be excessively bitter on the holidays. This is the time to observe and serve God in joy, and this will be our strength.¹⁷See Neḥemiah 8:10. There is a tension between joy and dread during the Days of Awe. Here, R. Salanter is instructing his disciples to tilt the balance away from dread by alluding to Ezra the Scribe’s admonition of those who were weeping on Rosh HaShanah that they should prepare festive meals and rejoice, for it is a joyous day. He is also responding to the doctors’ instructions that grief and mourning make the individual more vulnerable to illness, while joy strengthens resistance to the plague. The shift of balance from dread to joy is appropriate in a time of plague.

Take a good look at what is written here: וירא מנוחה כי טוב. This refers to the written Torah. ואת הארץ כי נעמה, ויט שכמו לסבול ויהי למס עובד. The words הארץ כי נעמה, refer to the oral Torah. The next few words refer to the willingness to shoulder the yoke of the Torah and to cleave to it by day and by night. The last words express the willingness to be G–d's servant to the point of weakening one's physical prowess.