There are fates which scare me more than death, more than permanent comas or disability, more than amnesia or dementia. It's suffering brain damage which would render me abhorrent to my former self. Examples I'm thinking of are Phineas Gage (took a railroad spike to the skull, and became a selfish fool) and Tila Tequila (suffered a stroke and became an unhinged 9/11 truther). From the perspective of my current self, it's metaphorically like I no longer exist, but a demon has eaten my soul and possessed my body.
Assuming I could quantify when such a thing happened in a legal sense, is there any way to force euthanasia in those circumstances? Obviously, in such a situation, the future "me" would claim they want to live, but the current me would, if I still existed, absolutely not want to live like that.
Is there a way to force myself to routinely undergo a sort of moral Voight-Kampff test, and end whoever it is claiming to be me if I fail?