In Existentialism is a Humanism, Sartre recounts a story of a student who asked him for advice. As the comic says, the student was torn between two paths, to stay with his mother, or to join the army and fight the Germans to avenge his brother and protect France. Sartre explain that no moral system, be it religious or philosophical, could tell him what to do. Abstract systems were too divorced from reality to answer such concrete, human questions. Sartre advised the student, rather vaguely, that he was free, and only he could make the decision - he could not defer to a system to make it for him. Sartre also claimed that the student chose him specifically knowing that he would give such advice. If the student had wanted Christian advice, he would have gone to a priest, etc.

We can imagine, of course, that the student didn't specifically seek out Sartre because he knew ahead of time that Sartre would advice him that the choice was his alone, and instead actually wanted some kind of concrete moral advice from a his philosophy professor. Perhaps, in this case, he would found to the advice of "well you are free so the choice is yours" to be quite lame.