Philippians 2:14-15

Do all things without grumbling or disputing, that you may be blameless and innocent, children of God without blemish in the midst of a crooked and twisted generation, among whom you shine as lights in the world…

An unthankful and complaining spirit is an abiding sin against God, and a cause of almost continual unhappiness; and yet how common such a spirit is. How prone we seem to be to forget the good that life knows, and remember and brood over its evil – to forget its joys, and think only of its sorrows – to forget thankfulness, and remember only to complain.