If you apply rationality to an overly emotional situation, it tempers the Emotions, resulting in clearer judgment.
Integrating the Mind’s data with the Emotions that were associated with it allows for a similar effect, evolving our emotional pool with rationality each time we’re submerging into sleep.
And even more significant, we are a separate conscious awareness viewing the world around us. In this way all our opinions, observations and conclusions that we've made throughout the day, are then integrated into the Body meaning into physical reality.
This is the energetic mechanism behind evolution.