In chapter 7 the wall has been built and the gates have been set. (By the way, you've heard the last from Sanballat, Tobiah and Geshem) Now most people make a fatal mistake in leadership at this point and would set back and would celebrate a job well done. But Nehemiah knows that the hardest part of the project has just begun.
Ask yourself: "What was the purpose of this project?" To rebuild the walls? Wrong. To restore Jerusalem! The walls was phase 1 in the project.
What did the project accomplish? It gave Nehemiah credibility to lead the people. Somebody had to know what he did for a living before he became governor (if you forgot - he was a butler). The project also gave Nehemiah momentum to lead. In order to change the culture of the land (from one of slavery to liberty) he was going to need all the credibility and momentum he could get.
In chapter 8 Nehemiah calls a town meeting where Ezra the priest reads the law of Moses. People began to weep because they realized that they were not doing what God wanted them to do! What contrast from 70 years prior! The generation that went into exile knew the Word of God and didn't obey it. The generation that came from the exile doesn't know the Word of God, but have a sincere heart to obey it.