Quality Time

The concept of quality time is very subjective. Quality of life is subjective as well. I hadn't really considered it until I was talking to a nurse and completing my Advance Healthcare Directive. It is a potentially daunting task.
The nurse asked a series of questions with the goal of determining your quality of life if you aren't able to communicate with your healthcare providers. In the case of the person being in a coma or vegetative state do they want to be kept alive with a ventilator or similar device.
The question becomes what kind of quality of life do you want? How does a person measure it?
The nurse told a story of a woman who cooked for her family and friends. Cooking was such a vital part of her life that she had to be in the kitchen cooking or life was not worth living.
So, the question remains. What do you feel is so important that your life isn't worth living without it?