What you call passion is not spiritual force, but friction between the
soul and the outside world. Where passion dominates, that does not
signify the presence of greater desire and ambition, but rather the
misdirection of these qualities toward an isolated and false goal, with
a consequent tension and sultriness in the atmosphere. Those who direct
the maximum force of their desires toward the centre, toward true being,
toward perfection, seem quieter than the passionate souls because the
flame of their fervour cannot always be seen. In argument, for example,
they will not shout and wave their arms. But I assure you, they are
nevertheless burning with subdued fires.

Hermann Hesse, from 'The Glass Bead Game'