Get up and go into the city, and you will be told what to do. (Acts 9:6)
Jesus started with Paul the way he would carry on the rest of Paul's life: he told him what to do. There was no appeal to Paul to submit and follow, only a command. The issue of the Lordship of Jesus was settled in Paul the moment he heard the voice and fell to the ground under the power of God on the road to Damascus.
That's why God achieved so much in Paul: there were no wasted years waiting for Paul's will to become one with God's. In a moment, in one encounter with the living Jesus, an independent, arrogant, cruel, self-willed, religious bigot became clay in the Potter's hands.