I also see that is rare cases it could be a mercy but I do agree in what the Church teaches. I have a complicated chronic illness which is effecting my lungs, liver, and kidneys. I am well now, in that I can still function day to day if I take it easy and pace myself. I’ve also battled cancer and will likely again.
With a lot of prayer I’ve already decided if I were to come to a point where invasive, complicated, painful, and drawn out treatment could only give me a chance I would most like choose to not do treatment and just live out my life as it is. I wouldn’t resort to euthanasia, but I can imagine wanting to at some point. But the sacraments are far too important to leave.