@quidcumque ah, I understand. Well, I think it might be an awareness thing that can help in the long run. So the kid learning to notice when its getting in the direction of a meltdown. In this case you can do that for them, when you know they are starting to get anxious. And then "feel" the feelings and observe them with curiosity and eventually coming up with individual coping strategies.
So for example my K2 always got really mad (screaming, hitting, destroying things) right after school. We sort of did the above and we came up with his solution, which is: whenever he feels like that after school, he eats the rest of his snackbox. And yes, that was a simple one, so maybe not the best example.
I think that this usually takes well into adolescence for bigger issues than the one in my example. I'm sorry that I don't have a better short term solution.