Cronin has really interesting ideas, but he gets Sartre completely wrong. Sartre never said that you can do anything you want, but that you always have only a certain number of possibilities to attain the goals you have set for you (and of course you can freely set your goals). They depend on the circumstances you are in. These circumstances become the "situation" in respect to acting to reach your goal in choosing one of the possibilities. Sartre even said that free will is above all - not accepting - but taking by decision the circumstances you find yourself in, to respond to them, to make the best of them according to your judgement.