People who have been raised in very emotionally turbulent homes, unprotected, with unpredictable patterns among the family members, or people who have been traumatised and have had this shock embedded in their physical and psychological patterning, people who have been through these experiences often remain very much under the influence of chronic fear. The Buddha taught that all sentient beings experience fear because they resist the impermanence of life. And this seems to support one of the findings of modern medical research and psychology, that the fear of death is our root fear. Researchers disagree with that now, but certainly the fear of death is one of the deep fears that we need to repress or suppress, So, we do have to suppress this fear or this awareness of our mortality, but to repress it is to push it into the unconscious, and then it just becomes another support for the brick wall of the ego.
( The Brick Wall of the Ego 2 by Laurence Freeman OSB )