One illuminating study compared the life success of high-school graduates and dropouts. It found that, though the former group did tend to do better, their success wasn’t due to higher intelligence.
Rather, they exhibited higher perseverance. This is what had enabled them to work through high school and also helped them deal with obstacles later in life.
Another study found that students who had attended a prestigious preschool went on to do better than their peers in many areas of life. But the difference didn’t come down to high IQ: at the preschool, they had picked up skills like curiosity and self-control, and these skills contributed to their success even into their forties.
So remember, it's not about being the smartest, it's about resilience and your will to succeed.