Lacrimae et gemitus naturaliter mitigant tristitiam, quia omne nocivum interius clausum magis affligit, quia magis multiplicatur intentio animae circa ipsum; sed quando ad exteriora diffunditur, tunc animae intentio ad exteriora quodammodo disgregatur, et sic interior dolor minuitur. (Et propter hoc, quando homines qui sunt in tristitiis, exterius suam tristitiam manifestant vel fletu aut gemitu, vel etiam verbo, mitigatur tristitia.)
Tears and groans naturally assuage sadness, because a hurtful thing hurts yet more if we keep it shut up, because the soul is more intent on it; whereas if it be allowed to escape, the soul's intention is dispersed as it were on outward things, so that the inward pain is lessened. (This is why when men, burdened with sorrow, make outward show of their sadness, by tears or groans or even by words, their sadness is assuaged.)
Secundo, quia semper operatio conveniens homini secundum dispositionem in qua est, sibi est delectabilis. Fletus autem et gemitus sunt quaedam operationes convenientes tristato vel dolenti. Et ideo efficiuntur ei delectabiles. Cum igitur omnis delectatio aliqualiter mitiget tristitiam vel dolorem, ut dictum est, sequitur quod per planctum et gemitum tristitia mitigetur.
Secondly, because an action, that befits a man according to his actual disposition, is always pleasant to him. Now tears and groans are actions befitting a man who is in sadness or pain; and consequently they become pleasant to him. Since then, as stated above (q38 a1), every pleasure assuages sadness or pain somewhat, it follows that sadness is assuaged by weeping and groans.
Augustinus dicit, in IV Confess., quod quando dolebat de morte amici, "in solis gemitibus et lacrimis erat ei aliquantula requies".
Augustine says (Confess. iv, 7) that when he mourned the death of his friend, "in groans and in tears alone did he find some little refreshment".