Repeated success in life is correlated with both those things, but they are not naturally correlated with one another. There are a lot of very smart people who

Repeated success in life is correlated with both those things, but they are not naturally correlated with one another. There are a lot of very smart people who dropped out of the race. Being smart can mean you don't need to learn grit, and maybe you never do; maybe the first hard thing comes, and you do something easier instead. There are also plenty of diligent hard workers who never amount to much more than a small business. Hard work isn't worth much on its own.