For our God is a consuming fire. (Hebrews 12:29)
When one is born again, you are filled with the Holy Spirit of God. This internal fire burns away any residual sin and convicts you of sin, meaning, if you are tempted to sin, it will stop you. And if you sin accidentally, it will help you to immediately repent.
Most assuredly, I say to you, unless one is born again, he cannot see the kingdom of God. (John 3:3)
But if one isn’t born again, then the next fire will be hellfire. It will also burn away your sin. But it continues eternally, since there is no repentance on the other side. It is the punishment.
For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord. (Romans 6:23)
Since sin is heavy and isn’t allowed into Paradise, we must lighten the load. The ancient Egyptians had a belief that the heart was weighed on a scale, and if it was lighter than a feather, one could move on to greener pastures. This myth is similar to being born again, although Messiah is the determining factor. He will help us through all things, both small and great.
Ask, and it will be given to you; seek, and you will find; knock, and it will be opened to you. For everyone who asks receives, and he who seeks finds, and to him who knocks it will be opened. (Matthew 7:7)