It is YOUR life. Not anyone else's. YOURS. You get to decide when and under what circumstances it will end, if it is at all possible to do so.
And I think it's sick and cruel that most of the world criminalizes people for wanting to control their own deaths. We force people to die is long, suffering agony rather than allowing them to choose euthanasia and die with some dignity. A lot of the time, they even ASK for death -- and many doctors oblige, in secret, at tremendous personal risk.
We give our animals more dignity than we give human beings. That's just sick.
But really, I don't think anyone needs to justify it if they wish to die. It's their life.
I think they should be subject to a brief psych crisis screening to rule out any treatable illness that can cause sudden psychosis, and then permitted to die either assisted or with effective and non-traumatic independent means.
People don't choose their birth. At the very least, they should get to choose their death.
We let people mark their bodies in various way, choose their lifestyle, choose abortion, choose all kinds of things, but not their death. And the reason we don't let them choose their death is because, ultimately, we think about the issue very selfishly. We think about in terms of how it might affect us, instead of in terms of how it might affect the person whose life it is.