Sanctification is an ever-gradual process of training. There is no “next level” as so many people like to frame it. Unless you are resistant to His work, or unless you are a carnal Christian at times in your life, not bothering to spend time in His presence and His word, then your walk should never be the leaps and jerks of constant turmoil in a life that resists submission. I know that there must be people like this. It only stands to reason since we are infinitely variable in our lives, situations, humility, and willingness. There will be Christians in heaven that cover the entire spectrum from “just got in by the skin of their teeth at the last minute,” such as the thief who was crucified beside Jesus, to the people like Mother Theresa or Pope John Paul or the many other wonderful people over the ages, including numerous martyrs, such as you might find recounted in Foxe's Book of Martyrs. They were totally sold out to Jesus and to loving service of those around them, holding to His truth and refusing to repudiate their faith even at the point of a sword. You may even know, may live around, or may even yourself be such as these who live out lives of loving service to our awesome God. There are so many that continue to serve Him faithfully, and there are so many that came before us that are like this, the so-called “cloud of witnesses.” There will be multitudes of us in Heaven who have yielded to God in the covenant relationship through Jesus and then the walk of sanctification. God’s banquet table is big enough for all who already served Him and are there in Heaven now and for all those who are currently living on earth and walking with Him and even for those that will yet answer to His call in the coming Tribulation.
Among those will be many legalistic Christians, who took the easy route of continued control rather than submission to His Lordship. There are several versions of the legalistic Christian that you may recognize. There is the head-hunter, ticket-punch Christian that modern evangelicalism made so popular. People who focus on just pushing the product of salvation but avoiding the greater demands of loving, humble service to those around them. It is so much easier to just focus on pimping the product that many of them do not even use themselves. But this fixation on just the point of salvation became so popular with modern evangelicalism as if getting people saved caused everything to fall into place. Being saved only starts the journey. There is so much to learn after that. By focusing so much on the moment of salvation, many churches turned themselves into salvation factories with many people coming in the front door, and just as many walking out the back door. They didn’t care because they had enough numbers coming in that they could boast of big budgets and numbers of people baptized as if the numbers were all that mattered.
They offered the tempting lie that you live happily ever after once you are saved, as if all problems in life stop at that point. I'm sure that some people took them up on this lie, maybe with many not really getting saved, not submitting their hearts and wills to God, just going through the motions as if this is just religion where you go through certain acts and rituals to earn your way to heaven. Or, there might have been people who really got saved but fell for the lie that life would be easy after that and became discouraged when it didn't, falling back into a carnal walk instead of taking their concerns to God where He would teach them and empower them to a stronger character that could deal with the problems of life. But the entire environment of legalism is exposed by the focus on the numbers rather than the complete package of broader truths required for living a Christian life. This focus on numbers is just evidence that pride is at work rather than the Holy Spirit. True, there are probably people saved even in that prideful, legalistic environment, but God can work anywhere He desires. He can even make a jackass speak to do His will, just as He did in the Bible.