R’ Simcha Zissel’s daughter was ill and went to the doctor who told her that the essential part of her cure was to remain calm.  Since her father, the Alter of Kelm, constantly stressed the importance of peace of mind, she happily told him that doctors cure physical illness with peace of mind.  Her father responded “You should have said to the doctor, ‘of course, peace of mind is needed, but please tell me how one obtains it.’”

Almost all doctors advise patients to keep calm and not get upset, but do doctors give a recipe how to obtain peace of mind?  A person who observes Shabbos with the proper attitude will have a taste of true peace of mind. ~ Chochmah Umussar, vol . 2, p. 204