If I might be so bold to respond.
Brother Paul Washer teaches that we can have the assurance of knowing that we're born again.
We'll walk in the way of the righteousness, on the narrow path that leads to the narrow gate, as a style of life. If you step off that path the Father will find you, give you reproof, and put you back on the path. (I John is a good book to use when we examine ourselves.)
But, if you profess to have gone through the narrow gate and you live in the broad way, just like all the other people who are carnal and wicked, the Bible says that you should be terribly, terribly afraid because you don't know God.
He gives an example: As an itinerate preacher, say he's invited to preach at a church. He arrives 30 minutes late and they ask him why he's so late. He says that he got a flat tire on the way and, while changing it, a lug nut rolled into the freeway. When he picked it up, a logging trucked barrelled down on him and hit him! That's why he's late.
The church folk tell him that can't possibly be true and the preacher asks why not. Because, you can't have an encounter with something as large as a logging truck and not be permanently changed by it! What's larger, a logging truck or God?
It's not by what's in our hearts, as so many in the church like to say. The Bible says that the heart is deceitfully wicked, who can know it? But, it says that you will know them by their fruits (plural).
Are we still walking, talking, and acting like the world? Do we enjoy the world's pleasures and experience the world's joys? Can we love sin and rebellion and not relish it? If this is the case, we do not know God.
A thorn tree cannot bear figs and a fig tree cannot bear thorns. If someone says otherwise, they're either a liar or crazy. So, those who call themselves Jesus' disciples and bear bad fruit, it would be the same thing.
1 John tells us that Christians do sin. They aren't without it. But the difference is that it's not their lifestyle. When they step off the path, God finds them, disciplines them and sets them on the path again. It's in the style of life.
I hope I've said something useful in all this. I'm not wise and I use too many words.