This can be a very tough topic for a lot of people to talk about. I would like to make one thing very clear before I get too far; this post is part of my personal challenge and I am in no way in any personal distress.
There are a few situations in life where we have a say in if it ends. The situation that pops into my head first is suicide. There are also cases such as signing a Do Not Resuscitate form if we are ever hospitalized.
As a somewhat grim person who often asks a lot of hypothetical questions, I have put thought behind at what point I would essentially pull the plug.
For myself, if my body were so sick that everyday was full of physical pain and I could hardly function, I would sign a DNR. I would also hope that if I had no brain activity that my family would make the call the unhook me from the machines. If possible I would want to be an organ donor so would only want to be kept on life support to keep my body healthy enough to save others.
Life is valuable and no matter how dark it gets emotionally, there is hope for it to get better. If you are having suicidal thoughts, please talk to someone about it. You are not alone and there is help available for you no matter how hopeless you feel.