It's important to note that pretty much every claim Duckworth has made about grit has been called into question by other research. That doesn't disprove it, but I think as a rule we should be extra skeptical of simple, easily-understood concepts that try to explain a complex world, or which even promise to give you control over it.

https://en.wikipedia.org/wiki/Grit_(personality_trait)#Scien...

She references Dweck's (Growth) Mindset as further reading. That is also at best questionable.