Set a beggar on horseback and he'll ride to the devil.

网络释义

1.	小人得意，忘乎所以 ... Set a beggar on horseback and he'll ride to the devil. 小人得意，忘乎所以。 Set a thief to catch a thief. 以毒攻毒。 ... cn.wordmind.com
2.	叫化子发财必然忘乎所以 ... Set a beggar on horseback and he'll ride to the devil. [谚]叫化子发财必然忘乎所以。 stubborn beggar 固执的家伙 ... dict.ebigear.com