The ego, whose identification is with the body, is terrified by death. The ego knows that with the end of the body, the ego is done, toast, no longer able to do its work in the imagined world of its host.
When it is realized that what we call the person is spirit and not a body, the fear of death loses its grip. The physical body dies but the spirit lives on in the stories that are told about the person in the memories of those left behind and maybe beyond.
A mature spirituality realizes that the spirit is immortal as the law of physics called thermodynamics teaches us. The energy of what we call the person is converted and absorbed back into the ground of being. We become one with the all.
What is at issue is whether we are consciously aware at death or "knocked out." If we are consciously aware at our death, our transition, we forgive others and become aware of forgiveness by them, and we surrender to the will of our Higher Power. When this conscious awareness of our "passing" occurs, there is great peace, if not joy, at going home to the oneness from which we sprang.
Obviously, there can be great grief on the part of others who will miss our bodily presence, and sometimes, we, even ourselves, may grieve the loss of these relationships in this incarnation.
The question is how will I die? Will it be in peace or distress? Will it be with a sense of completion or a sense of distress at wasted opportunities?
One of the huge benefits of a mature spirituality is a great peace and joy for a life well lived.