During earth life the energies of the soul team up with the ever changing energies of the material body. This teaming up of energies is not a one time event, because humans are given plenty of opportunities to develop their soul, and therefor, after a time of reflection in the astral world, they are able to use a new material body to learn through life and collect experiences. Because that, what the human soul has to learn in life, can hardly be learnt in a single lifetime, it takes many, many lifetimes. This Soul needs many of these tools in many different incarnations, to learn and experience the various aspects of life and thereby to develop and grow spiritually. Death is nothing definite, because there are many lives ahead of you.
Death is the removal of a tool that limits the view and awareness.
The transition of death is an awakening to the true self, to which nowadays only few people during life have access to.