Over the course of our relationship, my wife and I have attended a few Steven Curtis Chapman concerts. At each he talked about how it is important to know that God is great and God is good.
The simple prayer above, variations of which are myriad, starts with two very profound statements, rightly pointed out by Chapman. We often conflate the two, but really they are distinct.
God is great. God is powerful, mighty, able to save. God is above our complete understanding, and had to reveal Himself so that we could even have a partial (albeit sufficient!) understanding.
God is good. He loves, He is gracious, He works even the bad things out for good. He is holy, just and righteous; God is purely and definitively good.
Being great is one thing. But if God were not also good, we would serve a tyrant who would oppress His creation. It is good that God is, well, good, but if He were not also great His best intentions wouldn't be able to overcome the evil in the world. Were God not both good and great we'd be faced with a God who's a monster, or a God who's impotent in the face of evil.
In scripture this past week I've seen both attributes described within a few pages. Starting in Job, we see God's greatness. In Job 40-41, as in other places in this ode to God's greatness and sovereignty, God challenges Job by explicitly reminding Job of how far above Job God really is. (As an aside, I like seeing how people react when faced with the reality of God. In this case, Job responds appropriately in chapter 42, that is with humility.)
Turning a few pages over, in Psalm 16, we read, "I said to the LORD, "You are my Lord; apart from you I have no good thing." This is a psalm of rejoicing and steadfastness because God is good: faithful, providing, with us. (Aside here: David responds to God's goodness with joy, peace, praise and assurance. Again, a model response.)
God is great and sovereign, and we are in no position to judge Him. We can question Him for understanding; David did this in the Psalms. But we are not able to judge Him. But we need not judge Him, because He is good. He is good, He is great - and this leads to Him being trustworthy.
We can trust Him because He is good and able to do things to work things for good. You can't trust someone who doesn't have your best in mind (i.e., who isn't good) or who, despite wanting to, can't help (i.e., who isn't great.)
Let this be an encouragement in this time of financial strife, political discord and myriad other social ills. We have someone to whom we can go, someone who is both good enough to, and able to, bring good from even the direst circumstances.