Hey Leon, think of it like this:
We are alive and well and God has given us a choice. We can come to Him and apologise for the way we lived, and try our very best to live a new life in His Name.
Essentially:
You get caught speeding, and are asked to pay a £50000.00 speeding fine. You don't have £50000.00, and it will mean a life in jail, your life will be over. The judge however is a very good friend of yours, and loves you like a son. But he is a judge, and he absolutely must be righteous. So he fines you £50000.00 which you are forced to pay. He then steps down from the bench, and comes over to you, and writes you a cheque for £50000.00, and give it to you.
This is what God has done. Man was wicked, beyond reason and God (the judge) could not allow this to continue, so he flooded the world, and saved only the righteous who did His work. But He also promised that He would never do that again. Yet we continued to be wicked. This time, God came down to earth to teach us the right way, to show us how He would have us live our lives. Then He gave us an avenue to Him, through Jesus (think of him like the cheque for £50000.00). If we accept it, we can live in His name and be saved. If we
choose not to accept it, that is, if we think we can live life on our own, without Him, then we will be punished for it.
Basically, it's our choice. As to being forgiven after we have been offered a choice, that is like saying a parent will forgive a son after they have done something bad (sinned), and refused to apologise for it (rejected God). They will not, the son will be punished and that will be the end of it.
I hope that helps.
Digit