ERIK SPOELSTRA COULD have winged it. If anyone was qualified to give a talk on how to deal with a case of impostor syndrome, it was the former video coordinator who worked his way up to become head coach of the Miami Heat. But Spoelstra had come to know his young sharpshooter, Duncan Robinson, well enough to understand that a heartfelt speech about believing in yourself wasn’t going to do it. “I really wasn’t even a good high school player,” Robinson said. “I didn’t have any plays for me run in college — ever.”