Complaining and murmuring is the preset disposition of the natural man, and too often it becomes the preoccupation of our hearts. Thomas Watson reminds us where complaining and murmuring comes from:
Murmuring is no better than mutiny in the heart; it is a rising up against God. When the sea is rough and unquiet, it casts forth nothing but foam. When the heart is discontented, it casts forth the foam of anger, impatience, and sometimes little better than blasphemy. Murmuring is nothing else but the scum which boils off from a discontented heart. (Watson, The Art of Divine Contentment, 18)
The next time you find yourself complaining and murmuring remember, complaining is the overflow of a heart dissatisfied with God. A heart that is satisfied with God & His provision does “all things without grumbling or disputing” (Phil 2:14).