Definition
This idiom is used to warn someone that they will become uninteresting if they work all the time and never take time to relax or enjoy themselves.
劳逸结合，别只工作不娱乐（否则会变得单调乏味）
He's been working non-stop lately, with no time to relax. I think he needs to remember the saying 'all work and no play makes Jack a dull boy.'
他最近一直在不间断地工作，没有时间放松。我觉得他需要记住这句谚语『只工作不玩耍，聪明孩子也变傻』。
I'm worried you're working so late all the time; you'll become very dull. You need to rest more, remember 'all work and no play makes Jack a dull boy'.
我担心你总是工作到这么晚；你会变得非常无趣。你需要多休息，记住『只工作不玩耍，聪明孩子也变傻』。
The company has been so busy with the big project, I think employees need more time to relax. They need to keep in mind that 'all work and no play makes Jack a dull boy'.
公司最近忙于这个大项目，我觉得员工需要更多时间放松。他们需要记住『只工作不玩耍，聪明孩子也变傻』。