Throughout the Bible, God has come to designated people through a vision--Abraham, Jacob, Samuel, Daniel, Isaiah, Jeremiah, Ezekiel, and others. They usually responded (I'm saying "usually" but I think "always" might be true, but I don't want to look it up right now.
Paul immediately responds to the vision. He and his companions set sail immediately.
So begins the entry of the gospel story into Europe. I'm pausing here to imagine what Christianity would have been like if Paul had ignored this vision or, more importantly, what Europe would have been like.
We still are called to take the story into new places--let's be metaphorical here. Think about the Macedonias in our world, ones that don't require a long boatride, places with people who aren't like us, people we don't know, people who need the help of the church.
Tangent: Even after reading commentaries, I don't know what the significance of the change from 3rd person to 1st person means. Other 1st person sections in the narrative are 20:5-15; 21:1-18; 27:12-28:16).