Acts 20 gives the story of Paul's departure from Asia.
Paul reminded them how he lived among them, serving God with all humility and tears, and reminded them of the trials they went through when the Jews devised their schemes against him. Through all of this, Paul never stopped telling the good ways of Christ to them, teaching them both in public and in house to house. He said that his testimony to both Jews and Greeks was that of repentance to God and of faith in the Lord Jesus Christ.
Now, the Spirit was not only leading but constraining him and pulling him towards Jerusalem. He did not know the reason, but knew that the Holy Spirit testified to him in every city that brought both imprisonment and affections. This was not something that Paul wanted to value as precious towards himself, but only wanted to explain how he was led to finish the course God had put before him and spread the Gospel of the Grace of God that he received from Jesus Christ.
He knew that he would never see them again, so Paul gave his final warnings to them:
Pay close attention to yourselves. Elders made overseers by the Holy Spirit pay close attention to the flock. Care for the church of God, which Christ established with His own Blood.
Paul predicted that after he left, wolves would come in among the sheep. Not from the outside, but from among them men would start to rise up speaking twisted things to draw disciples after them. He told them to be alert, watching for this to happen -- because it would. For three years, Paul did not cease day and night to cry for each and every one of them for the day when the wolves would come.
As Christians, we should ask ourselves: Are we watchful of ourselves? Do we pay close attention not to become followers of men? Do our elders watch the flock, keeping them from becoming followers of men? Worse, have we became a minister that points to a man instead of pointing to Jesus Christ?