Then ask that person to be your agent for health care - someone you trust, someone who really knows you, your values, your very personal wishes. Your agent will not make decisions until, or unless, you lose the ability to do so. Your agent's main responsibility is to understand your beliefs and concerns about medical treatment. He or she also must be willing to make decisions that are consistent with your wishes. Your agent must be certain that treatment matches your wishes.
Guardianship is a judicial process in which courts appoint a guardian to make decisions.
That person, however, may not really know you or your wishes. It is better if you to select your own health care agent.