You know how this works. You are 8 years old and have your whole life ahead of you. There is no question whatsoever that you can realize your dreams just by remaining alive and getting through third grade. Career-path fantasies like becoming a fireman or a ballet dancer if you are a boy—an astronaut or a rock star if you are a girl—seem utterly within the realm of possibilities. Bring ‘em on, in fact. Never say never, your parents say to you over dinner. You can do anything, they reinforce in the car on the way home from little league. You begin to accept parental intelligence and acknowledge that anything is possible, and the bigger your dreams the better. Then, without warning, but as…