I don’t know too many unsuccessful people, to be honest, so it’s hard for me to evaluate the contrapositive. The few unsuccessful people I do know definitely show a pattern of not working as hard as the typical successful person I know.

I definitely agree that where you start has a huge impact on what’s possible. I am not saying that a really hard working villager in sub Saharan Africa is going to get better outcomes than the lazy child of an upper middle class family in the US.