When we truly turn to God in repentance through faith in Christ Jesus as Lord and Savior, we, at that time, have crossed from eternal death to eternal life (once and for all.)  We have an inheritance, as God's child, reserved for us in heaven that can never perish, spoil, or fade.¹

The Bible also says: "And you also were included in Christ when you heard the word of truth, the gospel of your salvation.  Having believed, you were marked in Him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God's possession - to the praise of His glory."²

Bible References:

¹ (1 Peter 1:3-4)

² (Ephesians 1:13-14   NIV)