The people of Israel gathered together on 24th day of the month (v.1). It was shortly after the feast. There, they repented their sins. It was initiated by the Word of God. What makes us to repent is nothing but the Word of God. Also, the Word must be preached to the humble and softened heart. Otherwise, people not repent but rebel. So in order for us to truly repent, we need to receive the Word with humble heart.
And this repent changes lives immediately. They separated themselves from the foreigners (v.2). It meant they intentionally broke the relationship with those who serve other gods, even thought it was costly. Then, they turned to God to worship.
Moreover, they made a covenant (v.38). And they made an oath, even binding themselves with a curse (10:29). Their repent wasn't a single event, but became a life-style. And true repentance must be continued throughout the life. It is not because our sins get bigger, but our awareness of our sin grows. And we become more desperate for the forgiveness of God, as we draw near to God.