Ezekiel 33:7-9 So you, son of man, I have made a watchman for the house of Israel. Whenever you hear a word from my mouth, you shall give them warning from me. If I say to the wicked, O wicked one, you shall surely die, and you do not speak to warn the wicked one, you shall surely die, and you do not speak to warn the wicked to turn form his way, that wicked person shall die in his iniquity, but his blood I will require at your hand. But if you warn the wicked to turn from his way, he does not turn from his way, that person shall die in his iniquity, but you will have delivered your soul.
Quite the startling text from the Old Testament as to the purpose of the church, but more importantly the duty of each member that makes up the Body of Christ. God will hold each of us accountable for missed opportunities in sharing His gospel truth to the world. It is amply clear that we cannot convict them, we can only present the truth from the earnestness of our heart, but the final decision rests with them. God does not coerce, does not twist their arm, and never forces the sinner in an effort to accept the Gospel truth. Instead He presents it clearly through the changed lives of His faithful followers. He gives to each of us the Holy Spirit to aid us in the spread of the gospel and give us understanding of the principles written in the Bible.
As a watchman for the church, it is our duty to keep on the lookout for lost and wondering souls. And then present to them gospel message. Then allow the Holy Spirit to do the rest.