Acts 13: 47 For so the Lord has commanded us, ‘I have placed You as a light for the Gentiles, that You may bring salvation to the end of the earth.’” 48 When the Gentiles heard this, they began rejoicing and glorifying the word of the Lord; and as many as had been appointed to eternal life believed. (NASB)
Paul felt convicted to do missions. He felt he needed to do it for two reasons. In this verse Paul is telling the church why he is there. He was there to preach. He was there because the Lord commanded him to be there. There is no greater sense of fulfillment in life when you realize why were born and that your life has meaning.
As a Christian we need to find fulfillment in knowing that God has placed us in this world to be a light. As Christians we cannot rest until we have preached the Gospel to everyone in this world. We know that not everyone will be saved, but we cannot stop trying to bring everyone to know Christ.