Ultimately, it is he Lord who helps people to hear, really hear, the message of hope in Christ. Paul knew that. His role was to speak at every opportunity. God’s role was to open hearts. The combination worked perfectly in the case of Lydia for whom “the Lord opened her heart to respond to the message spoken by Paul,” (Acts 16.14).
God designed it that way for Paul and for every ambassador for Christ. I must do my part and He will do His. Without God I can’t. Without me He won’t.