Here is a portion of a letter from Luther to his friend Philip Melachnton (June 27, 1530):
Those great cares by which you say you are consumed I vehemently hate; they rule your heart not on account of the greatness of the cause but by reason of the greatness of your unbelief. . . .
If our cause is great, its author and champion is great also, for it is not ours. Why are you therefore always tormenting yourself?
If our cause is false, let us recant; if it is true, why should we make him a liar who commands us to be of untroubled heart?
Cast your burden on the Lord, he says. The Lord is nigh unto all them that call upon him with a broken heart. Does he speak in vain or to beasts? . . .
What good can you do by your vain anxiety?
What can the devil do more than slay us? What after that?
I beg you, so pugnacious in all else, fight against yourself, your own worst enemy, who furnish Satan with arms against yourself. . . .
I pray for you earnestly and am deeply pained that you keep sucking up cares like a leech and thus rendering my prayers vain.
Christ knows whether it is stupidity or bravery, but I am not much disturbed, rather of better courage than I had hoped.
God who is able to raise the dead is also able to uphold a falling cause, or to raise a fallen one and make it strong.
If we are not worthy instruments to accomplish his purpose, he will find others.
If we are not strengthened by his promises, to whom else in all the world can they pertain?
But saying more would be pouring water into the sea.