"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
But it is precisely because of the work of Jesus Christ that we have hope. We have no fear of death because we can look at the grave and say, "you are not the end of me." Even more than this, Christians are ones who say, "More so, you bring into reality the greatest pleasure of my soul - being present with Jesus Christ." ("My desire is to depart and be with Christ, for that is far better" Philippians 1:22) It is this reason that we see why Christ is the propitiation for us, namely, "in bringing many sons to glory." (Hebrews 2:10) And to what glory you ask? The glory of of God in Jesus Christ - "Father, I desire that they also, whom you have given me, may be with me where I am, to see my glory that you have given me because you loved me before the foundation of the world." - John 17:24
There is more to the fact that we do not live in the fear of death. Those who have no hope of an afterlife live in fear of death, therefore they live constantly with the mindset "Carpe Diem" - or "no regrets" - or "Eat, drink, and be merry for tomorrow we die". But this is not the way Christians are to live. For such a long time I have lived in such a way that I look back constantly at my life and the mistakes I have made and look to not repeat those same mistakes. My whole life, in its essence falls into the same trap as the humanistic hedonist - Satisfaction of temporal pleasures. I do not want to pass up on the temporal pleasures that may come, and sometimes will justify things that appear to my mind as eternal pleasures but in reality are temporal.
The point is that I do not need to live by looking back in regret at the mistakes and missed opportunities that I have had because eternity will supply me with the greatest expanse of maximizing my joy that is found in Jesus Christ. This is exactly what Paul is demonstrating in Philippians 3:13-16 - "But one thing I do: forgetting what lies behind and straining forward to what lies ahead, I press on toward the goal for the prize of the upward call of God in Christ Jesus. Let those of us who are mature think this way, and if in anything you think otherwise, God will reveal that also to you. Only let us hold true to what we have attained." As Christians, we are not those who look back and lament at the sin and mistakes we have made and then proceed on those grounds. We are not saying "I don't want to miss any future opportunities, so I'm going to look back and see where I missed them in the past and make sure I don't commit the same mistakes." We don't think that way because unlike the humanistic hedonist - the opportunity to multiply that joy will come again because death is not the end for our experience of joy. And that opportunity is only found in Jesus Christ. We don't need to look back and hope we don't pass it up when it comes, instead we need to do exactly what Paul calls us to do - "Forgetting what lies behind and straining forward to what lies ahead".
The reality is that we have constant access to joy and glory, our enjoyment of it depends upon our view of attaining it. If we think we get it by constantly lamenting our past decisions and committing ourselves constantly to not repeating those sins and mistakes then we will never come to the present enjoyment of those pleasures, because our whole endeavor will be in what we are not going to do. But if we are constantly looking to Jesus Christ to satisfy us, looking through faith to see and lay the eyes of our hearts upon his glory, then we will not need to worry about missed opportunities for pleasure, only instead looking to the future of continual blessing of the experience of grace, glory and joy.
We are not held in fear of death because there is nothing that will bring our experience of joy to an end. There are, in the end, only those things that can increase our experience of joy, which is found in beholding Jesus Christ. We no longer need to live looking back in lamentation at our sin and mistakes, like what Paul lists in Philippians 3, because those moments are past and we can instead each moment indulge ourselves into the pleasure of beholding our Savior Jesus. There is nothing that can bring that to an end, not even death. And, like I highlighted before, not only does death not end our experience of pleasure, but instead, launches us into eternal blessed enjoyment of the constant multiplication of the experience of Joy as we, "see and savor Jesus Christ" - in the words of John Piper.
Do not fear death, it is not the end. Do not look back in regret because new opportunities to have the grace of God poured out on you is coming each new moment. Turn your eyes then to Jesus Christ and look full in his wonderful face.