Confucius (孔子), The Analects (論語), 7.36
The gentleman is always happy, while the petty man is bound and grieving.
The Gentleman (君子) is always happy because he has cultivated virtue within himself. Therefore, no matter what comes his way, he is steadfast and able to hold firm to the happiness (樂) within himself.
The petty man, on the other hand, lacks virtue, and is thus easily troubled and loses his peace at the slightest of incidents. He chases after the wrong things that not only do not benefit him, but leads to greater unhappiness. He is a slave to his vices, and finds himself grieving over the slightest of problems in each and every single day of his life.