The hardest thing emotionally would be:
Imagine being a 17-year old kid. Imagine a room, your mother lying on the couch, breathing with a lot of difficulty because of a really advanced stage of MS (muscle disease, eventually kills your respiratory system, and you die). The room is filled with family members, and a doctor. I'm standing behind the couch, trying to make sense of my feelings. Today, the doc is going to perform euthanasia on my mother... However, the family members disagree - she shouldn't do it! My mother should think of the children!
Now, imagine having to explain to those bastards that you *want* your mother to die, because you want to end her suffering...
(the story doesn't end there, luckily. The doc refused to do it without a final checkup in the hospital. My mother got some specific medication that had never worked before, and was actually for another disease, similar to MS. The medication worked. She's still alive today, healthier than she ever was during those previous years.)
(And I still feel tears coming up when thinking about that...
)