May not true believers, by reason of their imperfections, and the many temptations and sins they are overtaken with, fall away from the state of grace?
True believers, by reason of the unchangeable love of God, (Jer. 31:3) and his decree and covenant to give them perseverance, (2 Tim. 2:19, Heb. 13:20–21, 2 Sam. 23:5) their inseparable union with Christ, (1 Cor. 1:8–9) his continual intercession for them, (Heb. 7:25, Luke 22:32) and the Spirit and seed of God abiding in them, (1 John 3:9, 1 John 2:27) can neither totally nor finally fall away from the state of grace, (Jer. 32:40, John 10:28) but are kept by the power of God through faith unto salvation. (1 Pet. 1:5)
The Westminster Larger Catechism: With Scripture Proofs. (Oak Harbor, WA: Logos Research Systems, Inc., 1996).