Scripture emphasizes that preservation leads to perseverence.

John tells us that Jesus Christ, the Good Shepherd, is under promise to his Father (John 6:37-40) and to his sheep directly (John 10:28-29) to keep them so that they never perish. In his high-priestly prayer before his passion Jesus asked that those whom the Father had given him (John 17:2, 6, 9, 24) would be preserved to glory, and it is inconceivable that his prayer, which still continues (Rom. 8:34; Heb. 7:25), will go unanswered.
Paul sees the sovereign plan of God for the salvation of his elect as a unitary whole, of which the glorifying of the justified is part (Rom. 8:29-30). On this basis he builds the triumphant peroration of Romans 8:31-39, in which he celebrates the present and future security of the saints in the almighty love of God. Elsewhere he rejoices in the certainty that God will complete the “good work” that he began in the lives of those Paul addresses (Phil. 1:6; cf. 1 Cor. 1:8-9; 1 Thess. 5:23-24; 2 Thess. 3:3; 2 Tim. 1:12; 4:18). --JI Packer