In the magazine Total Film they have what is known as the 'predicted interest curve'. This is a way of assessing how happy the person is. The graph below is a kind of version of it. Instead of looking at a film, it looks at how entertaining a week is.
If you look at this graph you will see that there are three different experiences.
What kind of person do you think each person is?
Are they happy for a reason?
Do you have to be in a certain situation to be happy or entertained?
Situations that are commonly associated with 'quality of life'
Being in a hospital with a terminal illness or being raised in a difficult and poor homelife.
The difference a worldview might make
When it comes to talking about quality of life the discussion becomes more complicated. For example, if you are a Theist and believe that there is a Heaven where you will enjoy eternal blessing, you might be prepared to take more difficulty in the life than if there was no future beyond the grave. Someone who believes that Karma and Reincarnation are true might want to face the suffering now because they know that they will eventually face it if they end things sooner.