There is a thin line between Calvinism and Arminianism, and that thin line is perseverance. For the Calvinist, those who persevere prove they are saved, while those who do not persevere are not considered among the elect.
Arminianism holds that a person can lose their salvation. How is this done? Sin indeed separates, but the specific nature of that separation is the real issue. In Arminianism, sin ultimately results in losing one's salvation. We will leave it to the theologians of that camp to explain the many theories they offer on the matter.
The concept of perseverance, when it comes to the new birth in Christ, is always in question in both camps. Having studied this for over 50 years, I know you will get as many answers as individuals are holding these two views.
Our view is "once saved, always saved, never lost again." Sin in the life of a believer is dealt with in the present realm regarding discipline, while in heaven, it is strictly a matter of losing rewards—nothing else. Throughout my personal journey with these two "false" views, I have witnessed a never-ending battle among enthusiasts on both sides regarding the New Birth. Both sides will move heaven and hell to try to prove the other wrong and convince themselves they hold the higher ground. These two incorrect views are constantly clashing over the same issue: perseverance.
Those of us in the "once saved, always saved, never lost" camp are accused by both sides of belonging to the opposition. This alone is a testimony to their lack of clear thinking, as our view is neither. The reality is that the theology of these two views blinds them to a clear and correct understanding of this topic, and many others as well. This is an age-old issue that will not be solved here; that is between the factions who err. Those in my camp just shake our heads at their loss of the real security we have in Christ.
So, what is the problem? It is a matter of forcing ourselves to read, study, and outline God's word correctly within its context. We must let the author speak at all times and refuse to distort the real meaning of the text, as the other two groups constantly do.✔️