What does Deuteronomy 9:7-21 mean?

Remember and do not forget how you provoked the LORD your God to wrath in the wilderness. From the day you came out of the land of Egypt until you came to this place, you have been rebellious against the LORD. Even at Horeb you provoked the LORD to wrath, and the LORD was so angry with you that he was ready to destroy you. When I went up the mountain to receive the tablets of stone, the tablets of the covenant that the LORD made with you, I remained on the mountain forty days and forty nights. I neither ate bread nor drank water. And the LORD gave me the two tablets of stone written with the finger of God, and on them were all the words that the LORD had spoken with you on the mountain out of the midst of the fire on the day of the assembly. And at the end of forty days and forty nights the LORD gave me the two tablets of stone, the tablets of the covenant. Then the LORD said to me, ‘Arise, go down quickly from here, for your people whom you have brought from Egypt have acted corruptly. They have turned aside quickly out of the way that I commanded them; they have made themselves a metal image.’ “Furthermore, the LORD said to me, ‘I have seen this people, and behold, it is a stubborn people. Let me alone, that I may destroy them and blot out their name from under heaven. And I will make of you a nation mightier and greater than they.’ So I turned and came down from the mountain, and the mountain was burning with fire. And the two tablets of the covenant were in my two hands. And I looked, and behold, you had sinned against the LORD your God. You had made yourselves a golden calf. You had turned aside quickly from the way that the LORD had commanded you. So I took hold of the two tablets and threw them out of my two hands and broke them before your eyes. Then I lay prostrate before the LORD as before, forty days and forty nights. I neither ate bread nor drank water, because of all the sin that you had committed, in doing what was evil in the sight of the LORD to provoke him to anger. For I was afraid of the anger and hot displeasure that the LORD bore against you, so that he was ready to destroy you. But the LORD listened to me that time also. And the LORD was so angry with Aaron that he was ready to destroy him. And I prayed for Aaron also at the same time. Then I took the sinful thing, the calf that you had made, and burned it with fire and crushed it, grinding it very small, until it was as fine as dust. And I threw the dust of it into the brook that ran down from the mountain.