Being good at school is not the same as being smart. You can memorize the right answers but not understand how something works. I was very good at memorizing growing up. But I mistook memorization and good grades for being smart and knowing something. I knew the right answer, but I didn’t always know how to get there. I wasn’t thinking critically, and there is a big difference between knowing an answer and knowing something so well that you not only know the answer, but how to get the answer, can explain it in different ways, and understand the concept.