easier said than done
说起来容易，做起来难
口语·表示事情做起来比说起来难
英文释义
more difficult to do than to say; easier in theory than in practice
例句
Losing weight is easier said than done when you're surrounded by delicious snacks.
典故来源
源自古代谚语，强调理论上的简单与实际执行的困难之间的差距。