I have turned into the negative one. I criticise everything, I assume the worst of people, and I do not really enjoy anything any more. Can I come back from this?

“Why art thou cast down, O my soul? and why art thou disquieted in me? hope thou in God: for I shall yet praise him for the help of his countenance. O my God, my soul is cast down within me: therefore will I remember thee from the land of Jordan, and of the Hermonites, from the hill Mizar.”

The sons of Korah wrote this for someone cut off from the temple and from worship that had once carried him. He asks his own soul why it is cast down, and he does not answer himself with a scolding. He tells it where to put its hope, then admits in the next breath that his soul is cast down still. The psalm makes room for a person who cannot feel anything.

“Do all things without murmurings and disputings: That ye may be blameless and harmless, the sons of God, without rebuke, in the midst of a crooked and perverse nation, among whom ye shine as lights in the world;”

Paul writes to believers under real pressure in a Roman colony town and asks them to do everything without murmuring and disputing. The word for murmuring is the same complaint Israel made in the wilderness, the low grumble that spreads through a group. He is describing a habit that can take hold of a community, not handing down a diagnosis of anyone's character. He is not asking for forced cheerfulness.