Only God knows our hearts, and only He has the right to judge who will be saved and who will be lost. The Bible says that "he will judge the world in righteousness and the peoples in his truth" (Psalm 96:13).
And because only God is our judge, we must never put ourselves in His place and say that we know a particular person will definitely be lost. Even at the last minute, that person may turn in faith to Christ and be saved and then we would have been wrong. Jesus warned, "Do not judge, or you too will be judged" (Matthew 7:1). A prideful, judgmental attitude has no place in the life of any true Christian.
At the same time, one of God's greatest gifts to us when we come to Christ is assurance that our sins are forgiven, and assurance that we are going to heaven. We can't be proud of our salvation, because it is a gift from God. But we can rejoice that Christ has paid the full penalty for our sins, and we no longer need to fear God's wrath. The Bible's promise is true: "He who has the Son has life; he who does not have the Son of God does not have life" (1 John 5:12).
And this assurance can be yours! God loves you, and Christ died to open heaven's door for you. Don't refuse to accept the gracious gift He offers you the gift of salvation but by a simple prayer of faith, open your heart to Christ today.