-Jean Paul Sartre ...
(but maybe essence precedes existence?)
"It is inauthentic to refer to oneself through the eyes of others."
- Jean Paul Sartre
"One is not born a woman but becomes one."
- Simone de Beauvoir
"Man's greatness is his misery."
- Blaise Pascal
"One is never as happy nor as discontent as imagined."
- François de La Rouchefoucauld
"Those who live without madness are not as wise as they believe."
- Francois de La Rouchefoucauld
These come across a little more powerful in French...
But an idea is an idea!