The Triune Brain refers to three sections of the brain and their different aspects of functioning. The Frontal Cortex provides us with Executive Functions that make us human and able to have relationships. This area is responsible for us being able to remember the context of why we care about each other and about treating each other fairly.
They say that it only takes 20 seconds for the Amygdala to trigger Fight or Flight, which shuts off the Frontal Cortex. This is so we can react quickly from instinct to fight off an attacker or run away from a threat, without taking the time to overanalyze a situation. It takes 20 minutes for the whole brain to be reconnected and the Frontal Cortex to be available again. This is why we say things we don't mean when we are angry. Or rather we say things without a filter, and without the benefit of remembering the context of the relationship (we are friends or we love each other, etc.)