In the beginning, God created the heavens and earth. he created man and woman and a perfect world for them to care for and have dominion over. They walked with God Himself, learned about the universe from the One who created it. Yet they decided to question God--essentially rejecting His authority and therefore separating themselves from Him. It wasn't that they ate an apple--they chose knowingly to rebel against God. This was the first sin, that is, an act of rebellion against God. The result of that was exactly was exactly what Adam and Eve had been warned. Death entered into the world.
Maybe Adam and Eve didn't understand what death was because they had never seen it happen before. What were their thoughts when they saw the first thing die in front of them to provide them with clothing? With that image and the knowledge that the entire creation--the creation that was their job to oversee--was doomed to the same, it must have been heart-wrenching. Worse, they were cut off from the presence of God. They, like all of their descendants, were created to be with God and the emotional strain of their purpose and meaning being torn away from them must have been brutal. Since the first two humans first tried so long ago, mankind has been trying and failing to create its own purpose and meaning to replace what it lost.
God cannot allow anyone who has rebelled against Him to join Him. He prescribed the punishment as eternal death long ago and He must keep His word, because He is perfect. God did not respond to mankind's rebellion the way a human would, though. He responded in perfect love.
Becoming a man Himself, He took the full punishment of mankind's rebellion on Himself. As a man He could pay and as God His death was enough to pay for everyone. With Jesus dying on the cross, our debt to God was paid. With His resurrection, our meaning and purpose was restored. We can join Him.
See, a lot of people don't see any need for God. This is especially true in countries like America, where we are very secure financially and physically compared to much of the world. We think that we can live by the power of our own strength. And that is true, to an extent, but consider this:
I mentioned that God is holy and nothing impure or anything that has rebelled can join Him. Now, God judges us by our intentions, our attitudes, our internal thoughts more than by our external actions. The right deed for the wrong reasons is reprehensible. It also carries the same punishment because all sin, big and small, is a symptom of the larger sin of rejecting God's rule. This means lying, lust, jealousy, dishonest, anxiety, unkindness, and anything else short of perfect love and consideration for others. That's basically what being holy is--perfect love and consideration for one another, caring more for each other than yourself. None of us can meet that standard, so none of us can join God. We cannot make up that deficiency once we have rebelled. Because we've rejected God we are forever alienated from God unless He steps in and does something about it Himself, of His own accord. And that is where Jesus comes in.
If we believe that Jesus died and was resurrected for the payment of our own sins and seek to rejoin God through that payment, God considers our debt paid by that death. This kind of belief, if honest, does involve a drastic change in attitude. The Bible says that we are set aside by God to become His children, heirs to God's kingdom. This is the good news of the Gospel. This is the amazing love that Christians talk about--that God takes people who have openly defied Him and does immense work to bring them back to Him despite their indifference and open hostility. If you are not a Christian, this is the amazing work of God that you should hear. If you are a Christian, this is the amazing work of God that should bring back memories of who you were and what you've become and remind you of what He has done. We cannot bring any message greater than the Gospel; we cannot write a greater story than this.