This happens because people lack self-control and secretly love what's bad for them. It's dangerous to chase evil instead of good — because you might actually get it. Think about hunting wild animals. It's hard and risky work. Even after you catch them, they're trouble to keep. They often turn on their handlers and attack them. Great pleasures work the same way. They become great evils that take control of their owners. The more pleasures you have, and the bigger they are, the more you become a slave to them. Yet this is the person most people call 'happy.'
This arises from an exaggerated want of self-control, and a hidden love of evil: for it is dangerous for one who seeks after evil instead of good to attain his object. As we hunt wild beasts with toil and peril, and even when they are caught find them an anxious possession, for they often tear their keepers to pieces, even so are great pleasures: they turn out to be great evils and take their owners prisoner. The more numerous and the greater they are, the more inferior and the slave of more masters does that man become whom the vulgar call a happy man.