What does Nehemiah 8:9 mean?

Then Nehemiah the governor, Ezra the priest and scribe, and the Levites who were teaching the people said, 'This day is holy to the Lord your God. Don't mourn or cry.' The people had been weeping as they listened to the words of the Law. Nehemiah 8:9 - Modern Text Bible

(Hearing God's standards moves the people to tears, but the leaders remind them that this is a day for joy, not sorrow.)