Assurance is not what saves a person - The Christ provision is what saves a person.
Personally the condition of the saint has been changed by new birth.
Positionally the objective legal status of the saint has been changed by justification.
Progressively the subjective experiential status of the saint changes constantly. Assurance has to do with the subjective experiential changable status as it is dependent upon our continuing responses to God and others as well as to our self, the world and Satan. However, this is a battle to redeem our "TIME" not our entrance into heaven (Eph. 5:16-19). This is a battle to make our life count for the glory of God not to enter heaven. This is a battle for experiential blessings (assurance, joy, peace, prosperity, growth, etc.) not to enter heaven. This is a battle for future rewards that give an ABUNDANT entrance into heaven but not for entrance into heaven (2 Pet.1:11 with 1 Cor. 3:14-15). This is a battle to EXPERIENCE salvation here and now not to obtain it or maintain it. This is a battle for the salvation of our daily life and some days it is lost and some days it is gained.
When you read the last Biblical account of the Old Testament personage Lot, what do you read about? Drunk and committing incest. Can you find much of anything recorded about his life, and there is a lot, that provides fruit that he was a saved man? Not very much from the Old Testament. Yet, Peter informs us that he was a "vexed" with sin and he was a "righteous man."
He was "righteous" in regard to his inward new creation as it is created in true righteousness and holiness. He was "righteous" in his legal position before God. However, in regard to his EXPERIENTIAL life there is very little righteous that we can find and we certainly cannot find it in the last comments of his life.
He LOST his witness to his family - they would not heed his word. He LOST his wife. He LOST his self-respect with his daughters. He LOST nearly EVERYTHING experientially in life but the verdict of the New Testament was that he was not a LOST man. He is an example of a person whose soul was "saved even as by fire" (1 Cor. 3:14-15).
Our salvation is not determined by our EXPERIENTIAL life but by Christ's life. Our EXPERIENTIAL life determines our present joy, peace, assurance, witness, usefulness, rewards or EXPERIENTIAL salvation here and now.
The most miserable person in the world is a born again man in sin (Psa. 32; 51). David did not ask to restore his salvation but rather to restore "the joy" of his salvation or the SUBJECTIVE experience of the objective reality obtained by grace alone through faith alone in Christ alone.
HP: How can one be saved that has no assurance? If one comes to you with no assurance due to a lack of godliness, are you going to counsel such a one to overlook the lack of godliness and lay hold in faith to an assurance you say cannot be found apart from godliness?
If the Holy Spirit bears witness with our spirit that we are sons of God, who are we to even suggest that a proper relationship can or does exist where such a witness is not present as exhibited by a lack of assurance?