When you think about it, there is nothing else we face that is more monumental than death. This very thing trumps all other events in life because it throws up a permanent barrier to everything we know. It separates us from loved ones and prevents us from contact with them. Once we are dead, there is no turning back, no second chances, no changing our minds (in the case of suicide) and no way to undo what has been done.
If you are someone in chronic long term pain, there can be many times that the thought of ending your life is an immediate solution is seriously considered. The overwhelming thought of enduring the same pain without any hope of relief can be debilitating, to say the least.
If you are contemplating ending your life you are placing hope in the fact that you may soon be free of pain, religious considerations may or may not be pervasive at the time. Even just the notion that you can kill yourself and relieve the pain is in itself a sense of hope.
Now, consider how immensely troubling and terrible if you were to know that the same chronic pain you have will never end. You will be forced to endure it in the next 5 minutes and on and on without relief. It is hard to think of much worse condition than one without hope.
In the pit of depression brought on by pain, physically or mentally, it is really more about stopping the pain than anything else. you may have reconciled this event with God from the perspective that they are performing an act of love which they feel may end pain their illness or actions have caused others.
Of course, some may have convinced themselves that there is no God and therefore they are simply annihilated and cease to exist at death. This argument is a bit more perplexing since all civilizations have a sense of a God. Of course, if they have this understanding then they have already rejected God by their decision to disbelieve Him.
Regardless of the reasons, belief or justification an individual has used, one common event will occur. Once they have acted on their own death, it is irreversible, once they have pulled the trigger, kicked the stool, closed the garage doors or taken the pills, turning back is impossible if they have planned well.