Emotions are like muscles
Emotions are like muscles. They can be there when you need them. You can use them or not use them. But the muscles need to be exercised as well. An emotion is an initial reaction to an event that triggers you. The training of the muscle allows you to control your reaction to the trigger.
— from The Heart in the Cockpit (Emotion/Awe/Anxiety/Regret/Empathy)
In the book
That is all it is at the first instant — a reaction, not a verdict. Here is the image I have always found most useful: emotions are like muscles. They are there when you need them. — The Heart in the Cockpit (Emotion/Awe/Anxiety/Regret/Empathy)