4 sentences

1. 虚度光阴是人生最大的悲哀。

   xū​dù guāng​yīn shì rén​shēng zuì dà de bēi'āi.

   Wasting time is the greatest sorrow of life.

   Source: Dong Chinese Dictionary

2. 人生苦短，我们不该虚度光阴。

   rén​shēng kǔ duǎn, wǒ​men bù gāi xū dù guāng​yīn.

   Life is short; we shouldn't idle away our time.

   Source: Dong Chinese Dictionary

3. 不要虚度光阴。

   bù yào xū​dù guāng​yīn.

   Don't idle your time away.

   Source: Dong Chinese Dictionary

4. 老师常用这个案例来警示学生不要虚度光阴。

   lǎo​shī cháng yòng zhè gè àn​lì lái jǐng​shì xué​sheng bù yào xū​dù guāng​yīn.

   The teacher often uses this example to warn students not to waste their time.

   Source: Dong Chinese Dictionary