Full Idea
Sartre evolved from a notion of absolute freedom to one that truly takes into account the weight of situation.
Gist of Idea
Sartre gradually realised that freedom is curtailed by the weight of situation
Source
report of Jean-Paul Sartre (works [1950]) by Christine Daigle - Jean-Paul Sartre 2.3
Book Reference
Daigle,Christine: 'Jean-Paul Sartre' [Routledge 2010], p.57
A Reaction
This change seems to have come much later, in the 1960s. The main influence seems to have been Marxism, which claims that consciousness is created by society, rather than by free individuals.
Related Idea
Idea 22228 Sartre's freedom is not for whimsical action, but taking responsibility for our own values [Sartre, by Daigle]