The drug is used to improve the 'quality of life' for patients who have chronic illnesses. [=to make their lives more pleasant and enjoyable]
She has raised/improved her 'quality of life' [=she has become more successful] with her new career.
The restaurant serves food of high 'quality'. [=the food at the restaurant is very good]
(..) I will handle this side of the castle. Yes, sir! Hey Dean, on second thoughts, tell Professor McGonagall we might need one or two more wands this side. It is the quality of one's convictions that determine his success... ... not the number of followers. Who said that? Me. You okay, Freddie? (..)2011 Harry Potter and the Deathly Hallows: Part 2