There's a vote in the British parliament today about what they call assisted dying in which a terminally ill person with less than 6 months to live may be put to sleep as we say when we do it to animals. On the face of it, that seems a humane thing to do and I know for a fact that it has long been done anyway as both my grandfather and my uncle were doctors, and both told me it was standard practice in their day, which would have been from the 1920s to the 1980s, to give a dying patient an extra hit of morphine to hurry their passing. This was a decision doctors took on their own without consulting the patient or the patient's family. Imagine that now! But it was regarded as something that would ease suffering when death was inevitable but being dragged out. Of course, these days with modern medicine we can drag it out a lot longer, and maybe that is the problem. A protracted death is actually caused by medical advances.
So, from the purely human point of view it seems the right thing to do to allow people who are obviously dying to choose when they do die. Most of the objections are to do with coercion which clearly is an important issue, but it is not the only one or even, I would say, the main one. Very few people take the reality of God into account. If you believe in God and respect the traditional teachings about the illegitimacy of suicide, that puts everything in a different perspective. Because we live in a world of free will spiritual plans can be disrupted by human intervention but every soul does have a rough plan for its birth, life and death. Rough because it is not fixed in stone and must adapt to the soul's reactions while on this earth, but a general pattern nevertheless. It may be that our experiences at the time of our death form an important part of our experiences in life. In many cases we are thrown back on ourselves then in a way that is not possible at any other stage of life. To seek to prolong life through massive medical intervention may be one sort of wrong approach but to seek to cut it short may be another. Both are attempts to avoid one's destiny or soul purpose.
Having said that, it is hard to reach a conclusion when one is not in the terrible situation some people find themselves in during particularly severe and/or incapacitating illnesses, although even then if you believe in God you might think this is part of a soul's life lessons. Speaking for myself, I am unable to pronounce on the matter. I don't think we have enough information to make a correct decision. It's easy say that it is wrong but it could be countered that God has given us the opportunity to curtail unnecessary suffering at this time precisely because we have reached a point where we can prolong life past its natural point. All I would say is that every person who considers this should also consider the spiritual side of the question. For, when all is said and done, your body belongs ultimately to God and you should respect his will for you.