To know that you are eternally saved from the wrath of God because God says you are, in Scripture. To lack assurance does not change your eternal position in Christ. The purpose of Bible Doctrine is to solidify your faith so that you can be assured (confident) in your Eternal Security in Christ (Romans 8:29-39; Colossians 2: 6-14; 3:1-4). See “The Doctrine of Eternal Security.” See also “The Immutability of God.”
Think on this: Eternal Life cannot die! It is God’s life imparted to every believer in Jesus Christ. This is Grace!!