At what point is life not worth living?

What would have to happen to you for you to contemplate suicide or for you to ask to be euthanised. As you can tell, i'm talking about two very different scenarios. One where you may be depressed for some reason and may contemplate killing yourself. The other where you may have a degenerative illness and you have to give your consent for euthanasis or not. Something along those lines anyway. What would have to happen to you for you to want to die? e.g. your whole family dies, you are in a coma, your child dies, you lose your job....