While it is true that God predestines some to heaven, I personally don’t believe in double pre-destination, meaning that God predestines some to hell. While the elect are empowered by the Holy Spirit to believe, those who are ultimately damned are damned I believe by their free choice to reject salvation. God doesn’t tell us who the elect are, so we are to preach the gospel to all mankind. When God gives the effectual call, the elect will definitely respond with saving faith, but like I said, we don’t know who the elect are. So we give the gospel to everyone, even if they ultimately reject it!