The Exceeding Sinfulness of Sin

Romans 5:18 Therefore as by the offense of one, judgment to condemnation came upon all men, even so by the righteousness of One, the free gift unto justification of life came upon all men.
19 For as by one man’s disobedience many were made sinners, so by the obedience of One shall many be made righteous.
Come, let us reason together, brothers and sisters. God condemned all men from the sin of Adam. Sin is so horrendous, that God had to send his very own beloved Son down to live as a man, and become the sacrifice for our sins. Only that huge sacrifice could pay for all mankind's sins. Once Jesus had paid this enormous price, why then would God want us to return to sin? Why would he then shrug his shoulders and say "Oh well, they are at it again."
It should be obvious from the scriptures that God hates sin. Ask Uzzah, who steadied the Ark of the Covenant when it was going to fall and was struck down dead immediately. Ask Ananias and Sapphira who were struck dead for lying about the sale price of their property. Ask all those who died in the flood.
God's love is amazing. Even though we are all sinners, he offers us his mercy and grace. But God is also holy and righteous. He can't let sin go on forever. In the story of the prodigal son, the son had to repent and return to the father. The father let him go away to his sinful life and did not bring him back by force. The father waited until the sinning son returned in repentance and then showed amazing love for him by forgiving all. In each of us, we have the amazing opportunity to repent and be reconciled to God. In the world, God is giving us all the chance to turn to him, repent and be saved. But at some point he will say "Enough" and judge the world. In each of us individually, if we stray and sin, and do not return and repent, God will say, "Enough" and let us go.
If we lean on the Once Saved Always Saved doctrine (Which came from Calvin, the one who burned heretics at the stake) we are tempted to say of our sin, "Oh well, I'm saved. I can get away with just this one little thing." What we are really told is to live holy lives, because God is holy. Hebrews 12 Therefore, since we are surrounded by such a great cloud of witnesses, let us get rid of every burden and the sin that so easily ensnares us, and let us run with patient endurance the race that is laid out for us. 2 Let us keep our eyes fixed on Jesus, who is the author of our faith and the one who brings it to its goal. It says to strive to enter by the NARROW gate. "But the gateway to life is very narrow and the road is difficult, and only a few ever find it."
John 10:27 My sheep hear My voice, and I know them and they follow Me.
28 And I give unto them eternal life, and they shall never perish, neither shall any man pluck them out of My hand.
The Greek word for follow here is in the imperfect tense. This means that the action is ongoing. So it could read 'they follow me and keep following me'. So this promise of eternal life is given to those who follow and keep following. That would mean to try and live holy like God is holy. That would mean repenting when you mess up. Also note that the promise given to those who are following and keep following is that no man will pluck them out of his hand. That means no person can make you lose your salvation IF you're following Him. But it does not say and never says you cannot stop following. In fact, it paints a terrible picture for those who fall away and don't return. Hebrews 10:26 For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a terrifying expectation of judgment and the fury of a fire which will consume the adversaries. 28 Anyone who has ignored the Law of Moses is put to death without mercy on the testimony of two or three witnesses. 29 How much more severe punishment do you think he will deserve who has trampled underfoot the Son of God, and has regarded as unclean the blood of the covenant by which he was sanctified, and has insulted the Spirit of grace? 30 For we know Him who said, “Vengeance is Mine, I will repay.” And again, “The Lord will judge His people.” 31 It is a terrifying thing to fall into the hands of the living God.