He remembers being a child and his mother scolding him whenever he fell over, sighing at the scabs on his knees and the scrapes on his palms. Maybe if it happened less often, for reasons other than fighting, then she would've been more tolerant when Kyle came home all scratched up.
He hopes she would've understood this, because in this case there really is no other choice.
This is more than fighting, this is war, and to fight they've got to get the upper hand, some sort of advantage.
And that means blending it, whatever it takes.
So he takes the knife and drags it over his neck, as carefully as possible, knowing the wound will scar.
And this time that is what he wants.