Being totally honest here, I have to say that in the spirit of personal freedom, I should have the right to off myself given certain conditions:
1. That I suffer from a debilitating, progressive, chronic, and eventually fatal disease.
2. That said disease has been confirmed on multiple levels by competent, independent, and unbiased medical authority.
3. That prolonging my life reduces the quality of that life, and makes it increasingly difficult and unsustainable for my family.
Now, all that said, the dicey part is figuring out the "when". And obviously, who.
As I recall, Switzerland offers a facility where assisted suicide is performed. Those people make it a BUSINESS of offing people, so I question those kinds of places for obvious reasons.
A self-administered bullet in the head is messy and traumatic for the person who finds the body. Not good.
Poisoning - also not good, because it isn't always 100% effective.
There are several other options, all of which have their disadvantages.
But apart from the gift of life from God, I do believe that when things become untenable, it makes no sense to prolong my own life. That is a personal decision that I can and should be able to make after dutiful, protracted, and honest discussion with those closest to me.
This is why I have a "do not resuscitate" order in my revocable trust.
There is no way in hell I want to finish out this thing called life in a coma, or as a vegetable. Just let me go.