The sanctity of life should be valued over the quality of life. The quality of life will be different between people, and can not be judged the same. The sanctity of life is the same, so this should be the most valued. So you should value living over if the quality.
Because the quality of life is subjective an individual should always value the sanctity of life over it. The quality of life is subjective because what one considers quality, another does not. Therefore, it is better to love life as it is, rather than count it's worth by your possessions or your career advancements.
Of course it is up to each individual, but since we can be kept alive for so much longer in these modern times, we need to think very carefully about quality of life. Just living in a body is not sacred, after all. No one is going to live forever, and quality must be considered.