I choose my words rather carefully, unlike your rather careless dismissal of them. Seeing as backsliding is a matter of degrees, and must be judged in the light of accountability, and to be less close right now then you were at some point in the past means we are backslidden, then words of men defined falling from grace as, "willfully impenitently - despite warnings and chastisement - departing from the faith once held," making Christ of no effect, to no profit, drawing back to perdition, thus forfeiting what faith appropriated, which is what believers, as believers, are warned against. (Gal. 5:1-5; Heb. 3:12; 10:25-39)
Not because once again we are dealing with a besetting sin to our grief, or do not even know half the sins we committed. Again, it is faith that saves, being imputed for righteousness, and not because we perfectly achieved the latter (which Purgatory would not enable anyway. But as with our "father in faith, Abraham, faith in the Lord Jesus means, as I described, characteristically following the Him, and confessing sin with effectual repentance when convicted by conscience of doing or being the opposite. (Psalms 32:5, 6; 51:3; Hosea 5:15; 1 John 1:9)
And thus "we are judged, we are chastened of the Lord, that we should not be condemned with the world" (1 Corinthians 11:32) by dying impenitent.
Willful repudiation is different from falling into sin from what I can see.