First, dying isn’t an ‘act’; and second isn’t the moral thing to do to take each person’s case on its own merits?
Absolutely. Sometimes we should fight to make sure our loved ones get every bit of medical help they can. Other times we have to realize that they are not going to make it and give them pain relief and our love, while allowing them to go.
I despise the practice of assisted suicide (and the more common practice of killing through neglect) but when a person has a terminal illness it's OK to not take heroic measures.