The instinct to survive is hardwired into all of us. But with intelligence comes the ability to overcome instinct.
While not many of us would ever contemplate the possibility of ending our own lives, there are certain circumstances that might make death seem more desirable than continuing on.
One of these situations includes suffering from a terminal disease, especially one that involves continuous pain, discomfort or disability.
But according to Cardiff University, United Kingdom, professor of palliative medicine Baroness Dr Ilora Finlay, pain is often not the main motivating emotion behind a patient's desire to die; it is fear.
"Fear of the future, fear of what lies ahead - often based on bad experiences of what they have witnessed of death.
"Fear of being a burden - not wanting their family to remember them badly, and having to be dependent on others," she explained.
Those talking about assisted suicide - also called physician aid in dying - are often searching for a sort of insurance policy, a way out in case things get too bad, she said.
The request also often arises due to a lack of confidence in the healthcare system, where patients do not fully believe in the ability of healthcare professionals to see them through the course of their disease.
People think that having the option to end their own lives will give a feeling of some control over a situation that is often filled with uncertainty and helplessness.
Prof Finlay also noted that those who consider euthanasia tend to be better educated, high achievers, financially sound and not of an ethnic minority that is less emotionally bonded within a country. "I think it is the emotional vulnerability of the high achiever," she said.
Influencing the decision
Euthanasia is illegal in most parts of the world, including Malaysia and the UK, but some countries, such as the Netherlands and Belgium, allow doctors to inject lethal drugs under certain conditions.
Four American states allow physician-assisted suicide where the patient must drink the lethal drugs themselves.
Said Prof Finlay, who was the first palliative care consultant in Wales: "Making a decision to end your life is the biggest decision you can make. The risk of error is huge and the act is irreversible."
She added that the three elements crucial in making such a decision - both legally and personally - are accurate information, mental capacity and self-determination.
She noted: "It's very easy to be pressured into things. There is a pressure from society - it says, you are a burden, a pressure on resources. We live in a world that glamorises the young and fit."
Sometimes, the pressure can come from family members, who may not always be as loving and altruistic as expected.
Shared Prof Finlay: "I've been taken in by families that appear perfectly loving, only to find out later that there was money involved."
The attitude of healthcare professionals too, can exert undue influence on a patient's decision, conveying hopelessness rather than compassionate care.
Addressing the doctors and nurses in the audience of her talk on "End of Life Care - Relieving Suffering and Assisting Death" at Hospis Malaysia, Kuala Lumpur, earlier this year, Prof Finlay said: "I'm sure you've had experiences where you could persuade a patient in or out of treatment."
She added: "People trust us. We've got huge power over them. And we might have a bad day, and this influences the patient."
In Wales, where Prof Finlay chairs the government's Palliative Care Strategy Implementation Board, data on patients who were deemed to be on their last 48 hours of life has been collected for the past 12 years.
With over 26,000 cases to date, Prof Finlay stressed the margin of error in predicting when someone will die.
She noted that 3 per cent of those thought to be in their final 48 hours actually improve sometimes living for almost three months. And amongst those given a prognosis of weeks or months, some live well for many years.
The point, she makes, is that medicine is, in the end, still a probabilities game, and patients need to remember that while making their final decision on whether or not to check out of life.
In addition, she pointed out: "One-third of patients with neurological disease actually have decreased mental capacity, but they don't appear so until tested."
Dying of their disease
So, what can doctors do when a patient says they want to die?
Regardless of whether or not euthanasia is an option, Prof Finlay pointed out that doctors must listen to why a patient wants to die.
"You can ask, what is making today terrible? What can we do to improve today?
"And in all my years of working, it is always never more drugs. It is usually something else you can do."
She shared the story of a terminal patient on a ventilator who wanted to die, but whose root problem turned out to be her distress at feeling so unfeminine.
Once the nurses helped her freshen up, put on make-up and do up her hair, she was positive, saying, "I feel like a woman again."
"The subliminal message is that 'you are worth us working hard to improve things'," said Prof Finlay.
She also addressed the question of whether or not a doctor is killing a patient by stopping treatment.
"If the treatment is helping and achieving therapy goals, then carry on with it.
"But if it isn't, stop it. It's a waste of resources, and a burden on the patient and everyone around."
Sometimes, the patient will actually feel better after treatment is stopped, as the side effects are killing them faster than the disease. As Prof Finlay observed: "A diet of useless tablets is not good."
She said: "Of course, we should agonise over this decision. But if nothing is working and the best thing to do is to stop treatment, then it is really important to be clear, patients die of their disease.
"When you stop treatment, you are not killing them, they are dying of their disease - and they still need excellent care."