Today at work I had the opportunity to read what I consider to be perhaps the most succinct, yet crystal clear advanced directive I have ever seen.
"I wish to live and enjoy life as long as possible, but I do not wish to receive futile medical treatment that I define as treatment that will provide no benefit to me and that will only secure a precarious and burdensome prolonging of my life. I would also consider treatment futile when I had irrevocably lost the ability to interact knowingly and effectively with others. In general, I would, if competent, reject treatments that impose suffering or strain on me that were out of proportion with the benefits expected to be gained by the use of such treatments, even if my condition is not one that is specifically described in this instrument."
Compare this with the "standard language" in an advanced directive below.