This is also a blessed and useful habit and very effectual against the devil, who is ever about us, and lies in wait to bring us into sin and shame, calamity and trouble, but who is very loath to hear God's name, and cannot remain long where it is uttered and called upon from the heart. And, indeed, many a terrible and shocking calamity would befall us if, by our calling upon His name, God did not preserve us. 72] I have myself tried it, and learned by experience that often sudden great calamity was immediately averted and removed during such invocation. To vex the devil, I say, we should always have this holy name in our mouth, so that he may not be able to injure us as he wishes.
73] For this end it is also of service that we form the habit of daily commending ourselves to God, with soul and body, wife, children, servants, and all that we have, against every need that may occur; whence also the blessing and thanksgiving at meals, and other prayers, morning and evening, have originated and remain in use. 74] Likewise the practice of children to cross themselves when anything monstrous or terrible is seen or heard, and to exclaim: "Lord God, protect us!" "Help, dear Lord Jesus!" etc. Thus, too, if any one meets with unexpected good fortune, however trivial, that he say: "God be praised and thanked; this God has bestowed on me!" etc.,
Martin Luther, Large Catechism