To keep something in check 意思是約束，控制某事。

Keep emotions in check就是不顯露感情。

例句：

美國喬治華盛頓大學的研究人員說，A 15-minute walk three times a day after meals helpspeople in their 70s and 80s to keep their blood sugar levels in check. 每天三次飯后走15分鐘，有利于七八十歲的人控制血糖水平。

Bank Indonesia's newGovernor said that keeping inflation in check would be one of the centralbank's top priorities. 印尼央行新行長說，控制通貨膨脹將是央行的工作重點之一。

We must keep our spending in check this month．我們必須控制這個月的開銷。

Unless imports are kept incheck we are in danger of losing our favourablebalance of trade．如果不控制進口，我們就有失去貿易有利平衡的危險。

If I hadn't kept myselfin check，I might have saidsomething that I would have regretted later．如果我不控制自己的話，我就會說出一些以后要后悔的話。