Glad you started this thread Newtus i havent read much modern philosophy so I'm looking forward to the discussions! You've already prompted me to look at the context of your original quote and Sartre makes his meaning clear in this case by quoting Descarte: "conquer yourself rather than the world". If we try to adapt worldly things to our will, we are destined to fail because we can never account for all the possibilities involved in worldy endeavours.

I think it's also worth noting at the outset that all philosophies are a reaction to the thoughts and writings of previous eras, and a reflection of their contemporary culture. philosophy moves in trends and cycles and we can find parallels to existentialism in the stoics of ancient greece and rome, and even the humanists of the renaissance. Some modern philosohers will be aware of these parallels and some wont.