The Spirit’s work described in John 16:8-11 should infuse our ministry to sinners with tremendous hope. People we are ministering to can distance themselves and try to escape the conviction of the truth; they can attempt to tune out the guilty charges brought about by the Spirit through constant entertainment, or the intake of illegal substances or medications, but that cannot thwart the power of Almighty God.
They may not face him fully until they lay their heads on their pillows at night, but then, when he brings to mind their sin, they cannot escape their thoughts. We are to let the truth do its work as we minister to others in love and know all the while that the Spirit can regenerate a heart—even of the hardest variety—whenever he wants.
So if you ever are sensing you’re reaching a point of maximum discouragement in your evangelistic efforts with someone, remember you are not alone. It’s true that you cannot convict anyone of sin in their heart, but you have the Holy Spirit and he can testify to Christ through you to the heart of the one who is currently resisting.
Another consideration is that perhaps some of the discouragement occurs because we rely on our strength in our ministry to others or even our own methods. We sometimes think we can reason somebody into a saving relationship with Christ or if we do enough nice things for them, then surely they will see how great Jesus is and want to repent. However, unless the Holy Spirit does a saving work, then there is no SAVING work.
In all this we must keep in mind that this by no means everyone will automatically be convicted of sin and turn to Christ. Just because Jesus will send the Spirit to the world does not bring forth the salvation of the entire world. This has already been made utterly clear since the opening chapter of this gospel. One must be born of God and believe in Christ to be saved, but God has chosen to save through the means of our ministry of the word to others and through prayer. That’s what the Spirit uses to conduct this ministry of conviction.