Existentialism is a Humanism

I've been reading the article by Sartre and after going over some of it several times, it does make some sense. When he says 'there is no reality except in action' and 'Man is nothing else but what he purposes, he exists in so far as he realises himself, he is therefore nothing else but the sum of his actions' I can see that yes, basically that is true. However, people's actions can be constrained by factors outwith their control, sometimes people are forced into doing something they don't want to do, or do things because there is no other option open to them, or do things as a result of experiences they have had. I do not entirely agree that 'from the moment that he is thrown into this world he is responsible for everything he does'. As careers advisers then it is our job to help people to see that they do have choices, and that whatever situation they are in at any given time can be altered.