I remember visiting my grandmother with my new girlfriend when grandma was bedridden and nearly blind. She wasn't always lucid, but she was this time -- we had a nice talk about things in the past, she got to meet my girlfriend (who is now my wife), but during a lull in the conversation, she said "Johnny, I don't know why I'm still here, I just want to leave but my body won't let me".
That led to a long conversation of mortality with my gf and both of us promised that we'd help each other out if we got into that state and were ready to leave. I hope by then it's legal.