5 ideas
Alexander's horse Bucephalus panicked and could not be calmed, until Alexander saw it was frightened by its own shadow and turned its head toward the sun. Alain pairs this with a nurse whose baby screams: instead of explaining its character, she looks for the pin sticking into it. Both show that an apparent passion of the soul usually has a small physical cause, and that the fix is to find and remove that cause rather than argue with the mood.
Irritation, sadness and anxiety most often begin as fatigue, cramped posture, hunger or muscular tension, and the mind then invents reasons to justify the physical state. Because the reasons come after the feeling, arguing with them is useless. Acting directly on the body by yawning, stretching, relaxing the shoulders or walking dissolves the mood more reliably than thinking about it.
If left alone, the passions drift toward gloom, so pessimism is the default state of an unattended mind. Optimism is not a temperament or a reading of the facts. It is a deliberate refusal to follow the downward slope, and it must be chosen and renewed by an act of will.
Politeness works like gymnastics for the emotions. Gestures of civility such as smiling, greeting and moderating one's tone physically block the gestures of anger, because the body cannot perform both at once. The polite gesture comes before the good feeling and produces it, both in the person who makes it and in the person who receives it.
Moods spread, so displaying one's unhappiness imposes it on everyone nearby, while cheerfulness spreads as well. From this angle, being happy stops being a private matter of luck and becomes an obligation owed to others. Happiness is something you make and keep up, as a service, rather than something you wait to receive from circumstances.