Have you studied Gurdijeff's teachings known as "The Work" or read any of his books?

In Sufi and "The Work" essence is as you describe and it correlates to the light in the pranic tube that follows the spine. Chronic fear and/or anger can use up the light of the essence which depending on previously accrued light from past lives (if the light is too little) the essence cannot pass to the afterlife. The kesdjan body is the vessel for our spirit body fuel by conscious breathing and is supported by essence (in the Gurdijeff vernacular). It can be depleted.

After death of the physical body the kesdjan body is the temporary body on a mission for completion. Once the kesdjan body is completed (fill with light) the soul is made, and the person does not have to return to the Earth plane.