Vocation or self-invention

If every action aims at an end, and ends link up as means, then, on pain of infinite regress, there must be a final end willed for its own sake and never for the sake of anything else: this self-sufficient good is eudaimonia. What it consists in is settled by the function argument (ergon): as the flute-player has his excellence, the human has his own, the activity of the soul's rational part carried out in accordance with virtue. Happiness is therefore neither pleasure, nor honour, nor wealth, but an excellent activity unfolded over a whole life, whose highest form is contemplation.

The good of man is an activity of the soul in accordance with virtue, and if there are several virtues, in accordance with the best and most complete.Nicomachean Ethics, I.7 (1098a)

Nicomachean Ethics, I.7 (1097b) · Nicomachean Ethics, X.7

Lacking given values, the good is not received but made: it is the authentic existence that assumes its freedom and its project without taking refuge in bad faith or in a reassuring essence. The successful life is the one that lucidly realizes itself in action and engagement, more than a codified virtue or a pursued pleasure.

Existentialism Is a Humanism · Being and Nothingness, IV

Sartre denies any human nature: lacking a God to conceive it, there is no common essence fixing in advance what humans are. He does distinguish a human condition, the set of a priori limits of existence (being in the world, laboring there, dying there among others), which is not a given nature but the common frame within which each person makes himself. The position is therefore strongly culturalist, man being what he makes himself, not what he is by nature.

Existentialism Is a Humanism (there is no human nature, but a human condition)