Observation: Psalm 78 is a history psalm, meant to pass on to future generations the story of Moses, the escape of the Israelites from slavery in Egypt, and God's care for the people in the wilderness. The story is not told in a linear way, but jumps back and forth in time. Still, the heart of the story is that God keeps on providing for God's people, even when they forget, grumble and rebel.
Application: Too often my word for God is "what have you done for me lately?". I don't say it out loud or think it consciously, but I do get preoccupied with what I don't have, rather than what I do; with what God has not yet done for me, instead of the many things God has already done. Like the people of Israel, I say with my actions and thought patterns, "Yeah, water from a rock is nice, but what's holding up the entree?" I need to repent of my grumbling and rebellion, by giving thanks. A surefire way to head off my dumbest and most petty grievances is telling the story of God's work in my life and giving thanks.
Prayer: God, I woke up this morning in a warm house, surrounded by a loving family, with food in the fridge, with clothes to put on, and I am healthy. Thank you. Thank you. Thank you! Amen.