Because here’s the thing about anger: Once someone is already angry, it is not easy for that person to squelch it — even for adults.
“When you try to control or change your emotions in the moment, that’s a really hard thing to do,” says Lisa Feldman Barrett, a psychologist at Northeastern University who studies how emotions work.

But if you practice having a different response or a different emotion at times when you’re not angry, you’ll have a better chance of managing your anger in those hot-button moments, Feldman Barrett says.

“That practice is essentially helping to rewire your brain to be able to make a different emotion [besides anger] much more easily,” she says.
This emotional practice may be even more important for children, says psychologist Markham, because kids’ brains are still developing the circuitry needed for self-control.

“Children have all kinds of big emotions,” she says. “They don’t have much prefrontal cortex yet. So what we do in responding to our child’s emotions shapes their brain.”

Douclouff, M. & Greenhalgh, J. 2009. THE OTHER SIDE OF ANGER: How Inuit Parents Teach Kids To Control Their Anger. in NPR’s Goats and Soda. Stories of Life in a Changing World.https://www.npr.org/sections/goatsandsoda/2019/03/13/685533353/a-playful-way-to-teach-kids-to-control-their-anger

Interesting piece on how emotion regulation strategies are modelled between parents and children in the Inuit culture.