What is the relevance of existentialism (Sartre and Nietzsche) to the philosophy of well-being?

 
What is the relevance of existentialism (Sartre and Nietzsche) to the philosophy of well-being? Your paper’s thesis will establish the relevance by critically engaging with one of the theories of well-being we’ve studied (hedonism, Aristotle’s theory, or desire theory). The thesis might have this form:  This aspect of existentialism calls into question that feature of desire theory. A sample thesis (you may write about this, if you like): “The existentialist notion of self-creation calls into doubt the desire-theorist’s straight-forward focus on the satisfaction of desires as a way of increasing well-being.” Don’t write about marginal issues; make sure that what you explore is important in each theory. (if you write about Aristotle, your paper should be on the long side of the word count, because you’ll have to explain some central aspects of his theory, which are difficult to state briefly). 
At least 2/3 of your paper should be devoted to existentialism.
The target reader has not read any of these texts, so you’ll have to provide whatever background is necessary. Do not use quotations; use 
straightforward language

 
NOTE
The essay must be between 1600–1900 words (5–6 pages). Include a standard heading: writer’s name, assignment name and essay title (e.g., “Midterm Exam: Mapping Plato’s Divided Line onto His Cave Allegory”), department name, course name and number, professor’s name, date submitted, and word count. 
For this assignment, do not use quotations. Also, you ought to strive to describe the author’s ideas in your own words; do not rely too much on jargon. Be sure to use very plain language. You ought to strive to breakdown the ideas into the simplest, most straightforward terms possible; this involves thoughtful word-choice and uncomplicated sentence structure (but of course, you don’t want to simplify expression at the expense of accurately representing the details and subtleties of the concepts and arguments).