God won't let us rebel forever
God cares enough about humanity to take our rebellion seriously. He calls us to account for our actions, because it matters to him that we treat him, and other people, so poorly. In other words, he won't let the rebellion go on forever.
God's punishment for rebellion is death and judgement
The sentence God passes against us is entirely just, because he gives us exactly what we ask for. In rebelling against God, we are saying to him. ``Go away. I don't want you telling me what to do. Leave me alone.'' And this is precisely what God does. His judgment on rebels is to withdraw from them, to cut them offfrom himself--permanently. But since God is the source of life and all good things, being cut off from him means death and hell. God's judgment against rebels is an everlasting, God-less death.
This is a terrible thing, to fall under the sentence of God's judgment. It is a prospect we all face, since we are all guilty of rebelling against God.
How the Bible puts it:
He will punish those who do not know God and do not obey the gospel of our Lord Jesus. They will be punished with everlasting destruction and shut out from the presence of the Lord and from the majesty of his power. (2 Thessalonians chapter 1, verses 8-9)
Man is destined to die once, and after that to face judgment.(Hebrews chapter 9, verse 27)
Is that it then? Are we all destined for death and everlasting ruin? If not for God's own miraculous intervention, we would be.