I have to leave in a moment, but a quick response: Colossians 1:21-22: “And you which were in past times strangers and enemies, because your minds were set in evil works, hath he now also reconciled. In that body of his flesh, through death, to make you holy and unblameable, and without fault in his sight.” That is but one verse where it is made clear that justification occurs once. “Reconciled” is past tense - not future, not present progressive. Christ’s death has made us without fault - because of Christ’s sacrifice, not because of anything we have done or can do or will do. The warnings not to fall away in Scripture I can address later in full context but because of time constraints cannot do so now. I hope, however, that this thread can continue to be peaceful and not become acrimonious. Best to you.
You need to read two verses further: Colossians 1:24 Now I rejoice in my sufferings for your sake, and in my flesh I am filling up what is lacking 14 in the afflictions of Christ on behalf of his body, which is the church,
Christ’s death has made us without fault
But then answer the rest of scripture
"Whoever thinks he is standing secure should take care not to fall" (1 Cor. 10:11–12). How can you fall if you are without fault?
You indeed just might be saved: “Who gave himself for our sins, that he might deliver us from this present evil world, according to the will of God and our Father: Galatians 1:4 Might is a far cry from certainty.
And only IF you remain in his kindness. "See, then, the kindness and severity of God: severity toward those who fell, but God’s kindness to you, provided you remain in his kindness, otherwise you too will be cut off" Rom. 11:22–23 Clearly, you can be cut off. No certainty whatsoever.
And only IF you endure: Here is a trustworthy saying: If we died with him, we will also live with him; if we endure, we will also reign with him. (2 Tim. 2:11–12). So what happens if you don’t endure?
And only IF you stand firm: [Jesus said] “All men will hate you because of me, but he who stands firm to the end will be saved.” Mark 13:13 And what happens if you don’t stand firm?
And only IF you do what God wants: “God “will repay each person according to what they have done.” To those who by persistence in doing good seek glory, honor and immortality, he will give eternal life. But for those who are self-seeking and who reject the truth and follow evil, there will be wrath and anger. (Rom. 2:6–8). Clearly what you do matters.