My answer is based on my study of psychological and spiritual practices, FWIW.
Since Dying has 2 meanings here, one metaphorical and one literal, I’ll label each to make it clear which Dying I’m explaining. “How do we die (version A) before we die (version B)?” From here on when I say “die” I’ll be referring to version A.
What it means to die differs between individuals and exists on multiple levels of truth. Different areas of life and experience provide an opportunity to die and gain the resulting knowingness of immortality. Such areas often include: facing and conquering psychological issues (especially conscious re-visiting of trauma to release it), spiritual experiences such as kundalini as mentioned, facing any fear, connecting with your shadow side and utilizing its power which requires death of the old “innocent” self, using drugs to gain a widened perspective, and having a near-death experience. Any form of pain, facing of fear, and experience leading to acceptance of perceived negative conditions will develop this to some extent. “What doesn’t kill you makes you stronger.”
In each of these, before or during doing them, a great of fear of death is encountered. Upon bravely passing through it, one realizes there was a much wider scope of truth than previously realized and that the original fear was illusory. Upon consciously observing such experiences over a prolonged period, death as a whole is intuited as not so problematic as thought by the ego-self’s original perception. It’s a dialectic process - thesis being the comfort-seeking ego-self, antithesis being awareness of one’s impermanence and narrow perception, synthesis being an intuitive knowing of transcendence of death due to awareness of oneness with a much larger scope.
To provide a concrete example: a person with trauma lives in a struggle. The struggle of trauma continues because the trauma is trapped in the body and avoiding it doesn’t allow its release. The notion of facing and processing trauma seems like stepping straight into death. Choosing to engage in a therapy involving going into the trauma may feel like death during the process with great anxious trembling. But going through it and getting to the other side shows the person that the whole perception of fear was flawed from the beginning, and a misjudgement about what is actually a threat. When the fear was especially intense, its resolution can be extrapolated to questioning the reality of all death.
Another example is those who have died temporarily such as during a surgery. Many such people come back with an immense sense of peace. After dying, they report seeing great beauty and peace and then go on living with a new perspective that death is not the way it is commonly perceived.
