A: You have felt the deep dilemma that advances in medical science have imposed upon all people at the edge of life. Let's think together and pray together about what healing means in our time.
There are two forms of healing. One form (like treatment for pneumonia) eliminates the disease or pathology and hopefully makes the patient well again. The second form of therapy (like dialysis for people with renal failure) doesn't eliminate the underlying disease but enables the patient to live often years longer while enduring the effects of a chronic illness.
There's a third form of medical treatment that's not medical therapy. It's called palliative care and its sole purpose is to manage pain at the end of life. This is often done through hospice care at home or in a hospice facility.
According to all the major faiths, we're obligated to accept the two forms of real therapy. The reason we must allow ourselves to be healed is a foundational religious belief that God owns everything in the world: "The earth is the Lord's" (Psalm 24:1, I Corinthians 10:26) This world-ownership obviously includes our bodies.
Now, because God owns our bodies, we're not morally or spiritually entitled to kill what we don't own. Refusing therapy for yourself or your parents is killing what you do not own. Your question is complex, but the religious answer is bracingly simple.
This religious belief is the exact opposite of the common secular view that we own our bodies and therefore we ought to be able to kill ourselves (or ask others to kill us) when we're not satisfied with our quality of life. This is a basic moral choice about the way we view ourselves in the world.