It's not a topic most of us like to dwell on, but it's a reality many of us will have to face in the future - receiving the news from a medical professional that we have a terminal illness.
Now palliative care specialists have told The Atlantic's Jennie Dear what it's really like for a patient to be told they're dying, describing the trauma of the news as an "existential slap".
"The usual habit of allowing thoughts of death to remain in the background is now impossible," nurse and palliative-care pioneer Nessa Coyle from New York said, explaining that the crisis often occurs when a doctor delivers bad news.
However, it can also come at other stages, such as noticing the body is slowing down or observing other people's reactions to you, reports Daily Mail.
"It's not necessarily verbal; it's not necessarily what other people are telling you," she said.
"Your soul may be telling you, or other people's eyes may be telling you."
Whenever it comes, it inevitably provokes an "existential crisis" for the person in which they feel depression, despair or anger, or all three.
This stage doesn't tend to last and most patients tend to go back and forth between crisis and acceptance, according to palliative care specialist Gary Rodin.
According to Virginia Lee, a nurse who works with cancer patients, if people can come to a state of acceptance, they are usually more compassionate and appreciative of what life they have left.
However, this only works if they have fully faced up to the fact they are dying and are not in denial.
"It's like pretending it's not raining when it's pouring. You can do that when it's drizzling, but eventually, you have to live with the rain," she explained.
Research by the Dying Matters Coalition has found that a third of British adults think about dying and death at least once a week.
But the majority are still uncomfortable discussing the subject with loved ones, and fewer than 20 per cent have asked a family member about their end of life wishes.
When you die you know you're dead
Scientists have discovered that a person's consciousness continues to work after the body has stopped showing signs of life - meaning they have awareness of their own death.
A team from New York University Langone School of Medicine carried out twin studies in Europe and the US of people who have suffered cardiac arrest and "come back" to life, in the largest study of its kind.
Medically speaking, doctors define death based on when the heart no longer beats, which then immediately cuts off blood supply to the brain.
The brain's cerebral cortex - which is responsible for thinking and processing information from the five senses - also instantly flat-lines, says Dr Sam Parnia. This means that within 2 to 20 seconds, no brainwaves will be detected on an electric monitor.
This sparks a chain reaction of cellular processes that will result in the death of brain cells. However, this can take hours after the heart has stopped, he explained.
And performing cardiopulmonary resuscitation (CPR) that hasn't successfully revived a patient can still result in sending some blood to the brain - about 15 percent of what it requires to function normally.
But brain cell death is still happening, just at a slightly slower rate, he said.