Because God gives man eternal life through Jesus Christ, the believer is secure in that salvation for eternity. Salvation is maintained by the grace and power of God, not by the self-effort of the Christian. It is the grace and keeping power of God that gives this security. (John 10:29; II Timothy 1:12; Hebrews 7:25; 10:10–14; I Peter 1:3–5)
Man was created to exist forever. He will either exist eternally separated from God by sin, or in union with God, through forgiveness and salvation. To be eternally separated from God is Hell. To be eternally in union with Him is eternal life. Heaven and Hell are places of eternal existence.