To be gloomy before God is not pleasing to him, although he would permit us to be depressed before the world. He does not wish me to have a long face in his presence, as he says, ‘I have no pleasure in the death of the wicked’ [Ezek. 33:11] and ‘Rejoice in the Lord’ [Phil. 4:4]. He desires not a servant who does not expect good things of him.
“Although I know this, I am of a different mind ten times in the course of a day. But I resist the devil, and often it is with a fart that I chase him away. When he tempts me with silly sins I say, ‘Devil, yesterday I broke wind too. Have you written it down on your list?’ …Thus I remind myself of the forgiveness of sin and of Christ … He often troubles me with trivialities. I don’t notice this when I’m depressed, but when I feel better I recognize it easily. (Luther’s Works, v. 54, p.15)