"And they lived happily ever after..." That's how we like stories to end. After we hear about God, who He is, how He created us and the role He gave us in the world, it sounds so ideal. The problem is that we know that something has gone terribly wrong in the world around us. So what happened?
We have rejected God and His rule over us. We attempted to go our own way, do our own thing, rule over this world apart from Him, but we have failed miserably. We are rebels who want to live our own way rather than God's way. We thought we could do it without God. This rejection, rebellion and pride is what the Bible calls, "sin."
God takes our rebellion against Him seriously. Our sin separates us from Him. And being separated from God is not a good thing. He is the source of life and of all good things. God does not let us shake our fists in defiance at Him forever. There will come a day when every person will have to give an account of their life before God. Since we've told God, "Leave me alone!" That is exactly what He does and we are left to face His judgement for our sin which results in death and hell, eternal separation from Him.
"None is righteous, no, not one; no one understands; no one seeks for God. All have turned aside." Romans 3:10-12
"And just as it is appointed for man to die once, and after that comes judgment." Hebrews 9:27