I’ve posted before about the difference between grumbling and lamenting.  I just ran into another helpful delineation:

Lament is a cry of belief in a good God, a God who has His ear to our hearts, a God who transfigures the ugly into beauty.  Complaint is the bitter howl of unbelief in any benevolent God in this moment, a distrust in the love-beat of the Father’s heart.  (Ann Voskamp)

For more on this, see “Am I grumbling?” and “Are you still on the dance floor?”