I was very fortunate to be raised in a home where death and end-of-life care were not only not taboo subjects, but were openly discussed...
Dad understood what manner of end-of-life care could be given as the 'default choice', in the absence of truly informed decision making about that care. Our periodic discussions were not at all morbid, but took place in a context of 'what you truly need to understand about how people die'. The types of care likely to be offered were detailed and the pros and cons discussed. The quality of life was emphasized, and death was not presented as an enemy to be fought at all costs. The bottom line regarding whether or not certain types of dramatic medical intervention was warranted was tested against a very straightforward question: was whatever medical intervention being offered likely to lead to recovery and a quality of life that was reasonably enjoyable?
Both of my parents signed advance directives and gave me power of attorney for health care. They each made it very clear what they wanted done and under what circumstances. When the time came for each of them, my mind was at ease with the decisions I made, and that was a wonderful gift to me. Like anyone who loves their parents, I felt grief, but I was not burdened by guilt.
Although we're getting better about it, we still avoid talking about this subject, even though we should do so. Have the conversation with your loved ones, while you still can, rather than have life-or-death decisions forced upon them for which they are unprepared.