" Existential distress at the end of life bears many of the hallmarks of a hyperactive default network, including obsessive self-reflection and an inability to jump the deepening grooves of negative thinking. The ego, faced with the prospect of its own extinction, turns inward and becomes hypervigilant, withdrawing its investment in the world and other people. The cancer patients I interviewed spoke of feeling closed off from loved ones, from the world, and from the full range of emotions; they felt, as one put it, “existentially alone. "

― Michael Pollan , How to Change Your Mind: What the New Science of Psychedelics Teaches Us About Consciousness, Dying, Addiction, Depression, and Transcendence