I mean, I can't lie -- it sometimes seems appealing compared to the constant, gnawing sense that you might not be doing things good enough that comes with Christianity.
While that is a very common feeling, Christianity at it's core, is supposed to be an admission of inadequacy. "As a human, there is nothing I can ever do that will be good enough."
The corollary to this is that you want to do good because of your love for Jesus.
I can understand and agree with the moral and humanist teachings of Christianity, but the premise of "salvation through faith" always seemed fishy to me, pun only slightly intended.
No matter how much good a person does, or how much they try to lead a moral life, they're destined for an eternity of suffering because of humanity's innately sinful nature, because nothing imperfect can stand before God.
However, if they "believe in Jesus", then no matter how much they sin afterwards, they're good for Heaven, scot free?
If a secular system of law and order operated under these conditions it would be considered barbaric and corrupt.
I think many people on HN would agree that the point of prison is not revenge, but a mixture of punishment and rehabilitation that will hopefully deter the crimes of others and prevent future crimes by the convicted. We can't see into people's hearts and minds, so we must have standardized penalties. If we could really see into people's hearts and minds, and were sure we couldn't be deceived, we wouldn't let them out of prison until they were no longer the wicked person who would commit crimes, and we wouldn't keep them in prison once they had really changed.
In that case, the person who committed the crime is gone, and a law abiding, contributing citizen is there instead. We can't change the past, we can only change the future. This person is better in society than in prison. I think if we had the ability to successfully enact this system we would do it and it would be better than what we have now.
So the idea is God can really see into people's hearts, and doesn't want to just punish evil. He wants to redeem it, make what was evil good instead. So the story of Jesus is the story of how God made it possible for evil people to actually become really good, and once they have done so they can be in God's presence. And while they are still living on Earth, they will do good not because they are trying hard to follow the rules, but because they just want to.
With regards your second last paragraph, I'd recommend reading Romans, particularly chapter 8. You are right that those who believe in Jesus get off "scot free" but this is only because atonement is substitutionary. A Christian's sin is imputed to Jesus while Jesus' righteousness is imputed to him/her.
"believe in Jesus"
There must also be an entrusting of one's self to him, a yoking, whereby you give up "rule" over yourself and submit to his rule instead. To believe in Jesus but refuse to submit to him is rebellion. That's the state of demons and why demons are not saved even though they believe.
It is, unfortunately, the same state that many humans are in.
In addition to a trusting belief an attitude and acts of repentance must be present. Repentance is turning away from sin to God. This is a continual war for the genuinely saved because their sin nature is still present. They desire to serve God faithfully, but their nature has not yet been fully redeemed, so there is a constant battle going on to live to the Spirit and not the sinful nature (aka the flesh, see Galatians 5:16ff).
This is why most Christians really are hypocrites, with some being worse than others. They know the right way to live but do not do so perfectly themselves. Even the apostle Paul struggled with this:
"For I do not understand my own actions. For I do not do what I want, but I do the very thing I hate. 16 Now if I do what I do not want, I agree with the law, that it is good. 17 So now it is no longer I who do it, but sin that dwells within me. 18 For I know that nothing good dwells in me, that is, in my flesh. For I have the desire to do what is right, but not the ability to carry it out. 19 For I do not do the good I want, but the evil I do not want is what I keep on doing. 20 Now if I do what I do not want, it is no longer I who do it, but sin that dwells within me" (Romans 7:15-20).
However, if they "believe in Jesus", then no matter
how much they sin afterwards, they're good for Heaven,
scot free?
Also, as another commenter noted, it's not "scot free." Jesus suffered the punishment for all those who would come to believe. That is, God put their sin on Jesus and is now satisfied with the payment Jesus made. This idea is known as propitiatory atonement if you want to read more about the logic/justification behind it.
The only way to do things good enough is to, for lack of a better term, seek after Jesus. And then he works in your life, and that's the only way to "do the will of the Father". There are specific verses for all that, but to keep it short (and encouraging), just look up a few verses to Matthew 7:7-8 [2] "Ask, and it will be given to you; seek, and you will find"
One of my favorite things about Christianity is that even in this time with all of our knowledge and access to everything it is so widely misunderstood, in almost all of its principles people have almost the opposite conclusion from what was intended. It's fun to explain it, if I can assume I understood it correctly ;)
[1] https://www.blueletterbible.org/esv/mat/7/13/s_936013 [2] https://www.blueletterbible.org/esv/mat/7/7/s_936013