The reverse is also true...

An outgoing and rambunctious child is not always happy.

How does one gauge happiness in children? Is happiness in childhood the best gauge for productive and happy adult lives? Don't humans require a mix of things, both good and bad... happy and sad... isn't that how little humans learn that sadness and discontent are normal feelings? ...

and isn't allowing children to experience sadness and discontent a part of teaching them how to self-regulate their emotions... in order to grow up to be happy and content adults... who don't look over the fence with envy at the neighbor's green lawn over the septic tank?

https://www.goodreads.com/book/show/432288.The_Grass_Is_Always_Greener_over_the_Septic_Tank