You, dear mother, know the true source and foundation of your bliss, namely, the cornerstone, Jesus Christ, on which you should build your comfort in this and all other troubles. He will not let us fall or stumble, He will not abandon us or disappoint us. We call Him the Savior, for He is the Savior of all miserable sinners; all who are drowning in distress and death can rely on Him and call upon His name.
He says: “Be of good cheer, I have overcome the world.” (…) We are commanded to receive this comfort with joy and all gratitude. However, those who do not wish to be comforted by this word show a great injustice and deep disrespect to the dear Comforter…
“Be of good cheer. Be of good cheer, I have overcome the world.” That is the voice of the Victor, the true hero who grants me and assigns me His victory: “Be of good cheer!” On this I stand, I hold on to this word and comfort, I maintain this here and on the way to the other world; the Lord will not disappoint me. (…)
By our deeds, we cannot outplay sin, death, and the devil. Therefore, someone else stands here in our place and for us – He who has the trump cards in His hands and offers us His victory, urging us to accept it and not to doubt Him. He says: “Be of good cheer, I have overcome the world,” and elsewhere: “I live, and you will live too, and no one will take your joy away from you.”
(Martin Luther, letter to his mother, Easter 1531)