PASSION is produced no otherwise than by a disappointment of the desires, and an incurring of the aversions. It is this which introduces perturbations, tumults, misfortunes, and calamities; this is the spring of sorrow, lamentation, and envy; this renders us envious, and emulous, and incapable of hearing reason.
EPICTETUS. DISCOURSES. Book iii. §2. ¶2.
THIS faculty in particular we have received from nature, that whatsoever doth oppose itself unto her, and doth withstand her in her purposes and intentions, she doth, though against its will and intention, bring it about to herself, to serve herself of it in the execution of her own destined ends; and so by this though not intended co-operation of it with herself makes it part of herself whether it will or no. So may every reasonable Creature, what crosses or impediments soever it meets with in the course of this mortal life, it may use them as fit and proper objects, to the furtherance of whatsoever it intended, and absolutely proposed unto itself as its natural end and happiness.
MARCUS AURELIUS. MEDITATIONS. Book viii. 33.