Place it immediately after the clip that shows the foolish choice, then follow it with a reaction sound that answers the warning, keeping the warning as the turning point of the edit.
Sobre este sonido
This is a brief spoken line, lasting about a second, in which a voice delivers the words 'Don't be a fool' as a warning. The delivery feels blunt and cautionary, like a quick check on a bad decision before it goes further. It carries the name Half-Life in its title, and the line works as a short, pointed reaction rather than a longer speech.