Tristitia, inter omnes animae passiones, magis corpori nocet, quia tristitia repugnat humanae vitae quantum ad speciem sui motus, et non solum quantum ad mensuram seu quantitatem, sicut aliae animae passiones.
Of all the soul's passions, sorrow is most harmful to the body, because sorrow is repugnant to human life in respect of the species of its movement, and not merely in respect of its measure or quantity, as is the case with the other passions of the soul.
Est autem attendendum in omnibus animae passionibus, quod transmutatio corporalis, quae est in eis materialis, est conformis et proportionata motui appetitus, qui est formalis: sicut in omnibus materia proportionatur formae.
Now it must be noted that, in all the passions of the soul, the bodily transmutation which is their material element, is in conformity with and in proportion to the appetitive movement, which is the formal element: just as in everything matter is proportionate to form.
Illae ergo animae passiones quae important motum appetitus ad prosequendum aliquid, non repugnant vitali motioni secundum speciem, sed possunt repugnare secundum quantitatem: ut amor, gaudium, desiderium, et huiusmodi. Et ideo ista secundum speciem suam iuvant naturam corporis, sed propter excessum possunt nocere.
Consequently those passions that imply a movement of the appetite in pursuit of something, are not repugnant to the vital movement as regards its species, but they may be repugnant thereto as regards its measure: such are love, joy, desire and the like; wherefore these passions conduce to the well-being of the body; though, if they be excessive, they may be harmful to it.
Passiones autem quae important motum appetitus cum fuga vel retractione quadam, repugnant vitali motioni non solum secundum quantitatem, sed etiam secundum speciem motus, et ideo simpliciter nocent: sicut timor et desperatio, et prae omnibus tristitia, quae aggravat animum ex malo praesenti, cuius est fortior impressio quam futuri.
On the other hand, those passions which denote in the appetite a movement of flight or contraction, are repugnant to the vital movement, not only as regards its measure, but also as regards its species; wherefore they are simply harmful: such are fear and despair, and above all sadness which depresses the soul by reason of a present evil, which makes a stronger impression than future evil.