Appetitus delectationis est fortior quam fuga tristitiae quia naturaliter maior est appetitus delectationis quam fuga tristitiae.
The desire for pleasure is of itself more eager than the shunning of sadness because desire for pleasure is naturally greater than the shunning of sadness.
Cuius ratio est, quia causa delectationis est bonum conveniens, causa autem doloris sive tristitiae est aliquod malum repugnans. Contingit autem aliquod bonum esse conveniens absque omni dissonantia, non autem potest esse aliquod malum totaliter, absque omni convenientia, repugnans. Unde delectatio potest esse integra et perfecta, tristitia autem est semper secundum partem.
The reason of this is that the cause of pleasure is a conforming good; while the cause of pain or sadness is an unconforming evil. Now it happens that a certain good is conforming without any repugnance at all: but it is not possible for any evil to be so unconforming as not to be conforming in some way. Wherefore pleasure can be entire and perfect, whereas sadness is always partial.
Alia vero ratio est, quia bonum, quod est obiectum delectationis, propter seipsum appetitur, malum autem, quod est obiectum tristitiae, est fugiendum inquantum est privatio boni. Quod autem est per se, potius est illo quod est per aliud.
Another reason is because the good, which is the object of pleasure, is sought for its own sake; whereas the evil, which is the object of sadness, is to be shunned as being a privation of good: and that which is, by reason of itself, is stronger than that which is by reason of something else.
Bonum est fortius quam malum, ut patet per Dionysium, IV cap. de Div. Nom.
Good is stronger than evil, as Dionysius declares (Div. Nom. iv).