Trigger warning on this post: I discuss suicide very directly as someone personally familiar with it, and this topic is all about suicide (euthanasia and suicide have no distinct boundaries that separate them).
I mean, to some extent, we do have that right: suicide isn't criminalised
can you fkn believe that a suicide attempt used to receive the death penalty?! 
, though you can be involuntarily committed to a psych ward and/or suicide watch and your life saved directly against your will.
While I in no way believe suicide to be a "sinful" or "selfish" or "cowardly" act, it does have an incredibly huge impact on others. Like, huger than the sufferer could possibly imagine. I compleeeeeetely don't condemn those who attempt suicide (or I'd be condemning myself), but I don't feel a life belongs only to you: it also belongs in some part to all who love you, so no, I don't believe you have the simple right to take it whenever you choose. It is in some way taking part of the life of many others, if that makes sense? I think one does owe others something, though that can be lost when the pain is simply unbearable.
Euthanasia is essentially deciding that life will no longer ever have enough good to be worth going through the predicted bad (illness, pain etc).
But as everyone else has said - that's identical to the illusion mental illness tends to create, and mental illness is treatable and improvable. Where do you draw the line and decide when that's a truth, and when it's a lie?
What are your thoughts, ____?