Practice is from position, never to position. The ethical mandates of the New Testament are decisively clear that believers are to walk in the richness of the position we have been given (Eph 1:3), and that the position is actually necessary for the walk (Heb 11:6). Never is a believer warned that their position as a child of God is in danger because of their walk.
Certainly there are warning passages. Hebrews 4:1 warns us to fear lest we “may seem to have come short” of entering His rest. Hebrews 4:11 prescribes diligence so that “no one will fall.” In the same context, the writer exhorts, “let us draw near with confidence to the throne of grace, so that we may receive mercy and find grace to help in time of need” (Heb 4:16). Why else would we need continuing grace and mercy if we were without sin in our practice?
Later, the writer reminds, “we are not of those who shrink back to destruction (Heb 10:39). There is no future of destruction for believers because “the believing one has eternal life” (Jn 6:47). Once eternal life is given, then by definition, it is eternal. Any end to it would make it something other than eternal.
The warnings, then, are not about loss of position, but about loss within that position. One whose practice is lacking will suffer loss—even losing reward—but that person is still secure in position (1 Cor 3:12-15).