“Since therefore the children share in flesh and blood, he himself likewise partook of the same things, that through death he might destroy the one who has the power of death, that is, the devil, and deliver all those who through fear of death were subject to lifelong slavery.” Hebrews 2:14-15
Jesus came to this earth to die, and by dying He was able to conquer death in His resurrection, and by conquering death, he made Satan powerless against everyone who’s saved. For the believer, “death is swallowed up in victory” (1 Cor. 15:54) Through Christ and His work, we are not to be afraid of death anymore! The fear of death and it’s spiritual bondage has been brought to an end.
“For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, "Abba! Father!" Romans 8:15
If you aren’t a born again Christian, you are slaves to your fear of death (Hebrews 2:14-15) and your final punishment (1 John 4:18) because of your life of sin. But if you have been born again, Christ has adopted you as His son/daughter! And because you are His child you can come before Him without fear or hesitation as our beloved Father, and once you are saved and have repented from your sins you can have confidence that you are truly a child of God. The term “Abba” conveys a sense of intimacy, and is the equivalent to “Daddy,” and this indicates tenderness, trust, and a relationship free of fear.
The only way you can become God’s child is through spiritual adoption, and that is putting your faith and trust in Jesus Christ, and repenting (or to turn away) from your sins. Until you have been adopted as God’s child, you are a child of Satan and will live your life as a slave to fear. Unrepentant sinners will live in eternal life of torment, but in Christ, you are promised life everlasting in paradise, if you just put your faith and trust in Him and allow Him to do a work in your life.