Advances in medical technology mean, plain and simple, that people's lives can be sustained even when they are terminally ill and have no hope of leading an active, independent life. An advance directive is a document in which you give instructions about your health care and what you want done and not done if you can't speak for yourself. Advance directives are not complicated, typically consisting of short, simple statements expressing your values and choices. "Advance directive" is a term that includes health care directives, living wills, health care (medical) powers of attorney, and other personalized directives.
An advance directive, including a health care (medical) power of attorney, has no legal effect unless and until you lack the capacity to make health care decisions or to give consent for care. By expressing your wishes in advance, you help family or friends who might otherwise struggle to decide on their own what you would want done, a point that was amply illustrated by the Terry Schiavo case. Finally, advance directives aren't just something for old folks. The stakes are actually higher for younger people in that, if tragedy strikes, they might be kept alive for decades in a condition they would not want. Everyone should consider preparing an advance directive; it can provide comfort to family members at a difficult time. Also, an advance directive can save a lot of money. The cost of keeping someone alive by artificial means can drain a family's estate.