Explain Like I'm Five

This is rather like asking Asians why they all eat white rice when brown rice is healthier.

Not all Christians believe either one of those things. And for those that do, the answer is generally that trying to follow God and be obedient to His will is a sacrifice of gratitude to Him for His sacrifice of salvation.

OK so he died for nothing if NO ONE sinned... so just sin a little because he purified the human race through his sacrifice so don't make his suffering worse... (It's hard to logic this way but if you truly thought your sins were purged by his crucifixion, you might make an economic argument out of it).

The point of the new. Testament , meaning the new pact was to free up Jewish believers from the very strict rules and requirements of worship to attain gods good graces. The whole idea of forgiveness was mainly aimed to free you up to actually do some of the good things required to achieve what you might be praying for, rather than just sit in temple and hope for the best by gods will alone.

On a core doctrinal level for Catholicism, Christians should strive to emulate Jesus as best you could to help build the kingdom of heaven in this world already, rather than just wait for the after life. They are also bound to obey the laws and be good citizens. It really all boils down to don't be a dick.

The promise of forgiveness was aimed, in historical context, at loosening the strict requirements of Judaism and also to allow for non believers that lived good lives to be considered saved, to allow Christians simpler coexistence than it might have been..

Obviously you will rarely if ever find anyone living like that in actuality.

Raised Catholic, not my jam. But as I understand it, if you go to confession without being truly sorry and having a sincere intent not to sin again, it doesn’t work. So if you’re going in with the attitude that confession is basically insurance against hell and you can just use it to get everything fixed up at the end of your life, but you’re also knowingly neglecting your soul and have the intention deep inside to be a jerk and keep sinning, God’s gonna be like “sorry, we don’t cover that” and deny your claim.

God doesn't tell us not to sin because he's trying to boss us around. God tell's us not to sin because sin is it's essence, self destructive and contrary to our own good. We can be forgiven ultimatley upon our death and go to heaven, and also live a miserable life because of our own sin here on Earth. Note that this does not mean, that if you don't sin (very difficult i hear) that you won't have issues in life. It rains on the just and the unjust and we live in a fallen world that is ravaged by sin. It's just that we can remove a large portion of the problems that are self inflicted by living in an upright way.

Hope that perspective helps

I'm not a Christian, but my wife is so we talk about these types of questions a lot.

You don't "have to be good." You have free will. However, there will be consequences after death depending on what you choose.

"If Jesus will forgive you no matter what" is not accurate. To be forgiven, you have to truly repent for your sins. Only you and God know if you are truly repentant. Would you consider yourself truly repentant if you did something bad because you expected to be forgiven? I mean remember, God is supposed to be omniscient.

Attempting to abuse the system itself would be a sin. But that could be forgiven as well if you truly repented for it.... So all in all, Christianity offers anybody hope for forgiveness, but we have no way to know who is actually forgiven in the end. That alone should be enough argument for erring on the side of caution and not sinning (assuming you accept the stated rules of the system).

God will only forgive you if you repent. You can't be a dick all your existence, say "Please forgive me at the end" without truly beliving it and that's it.

It's all about how you arrive at the pearly gates. You could live a sinful life of you truly redeem yourself on your dying bed; accept Jesus and free yourself of your sinful ways.

The strategy of living sinfully with last minute redemption comes with two big drawbacks. First, death could come for you at any moment - you won't necessarily have time to prepare. Second, your conviction in time of dying needs to be sincere. It would be impossible to fake, and most sinners probably wouldn't even know where to start. That's why it's all but impossible for rich people to get to heaven - their minds are twisted towards justification of their inaction, and their chance of redemption is close to zero.

That's my understanding anyway, I'm an atheist from a Protestant country living in a Catholic one.

God will forgive who he chooses to forgive, but of us we are required to forgive all. Implicit in this is that God's forgiveness is not automatically given to everyone. It is offered to everyone freely. Christ has already paid the price, but it is up to us to accept that gift and repent of our sins. Not repenting means that well suffer for those sins in the afterlife, but doing so won't mean we then get to go to heaven. Our reward is dependent on how we lived up to the truths we understood in life. Christ invites us to repent and live a higher life, a holier life, a life of continual repentance.