tighten one's belt是“勒紧裤腰带”的意思，按照我们中国人的理解，其引申意思就是“节衣缩食、节约度日”。

【例句】
Tighten one's belt I spent too much money last month. I better tighten my belt this month or I will be in trouble.
我上个月花太多钱了，我这个月最好缩衣节食点，否则我就糟糕了！

He tightened his belt only in order to pay for his tuition fee.
他省吃俭用，只为了付得起自己的学费。