I suspect that happens a lot more often in movies than in the real world. In the real world you have to figure out if you will be able to make a living off your passion, raise a family in the near future, save some money and tend after your parents in their last years (depending on your culture YMMV).

Of course, every once in a while you hear about somebody who did exactly that and it worked out for them. It that an exception or the norm?