总有那天苍了少年老了天真
[zŏng yŏu nèi tiān cāng le shăo nián lăo le tiān zhēn]
"Zong you na tian cang le shao nian lao le tian zhen" which means 'That day will always come, the youth turns gray-haired, and the innocent gets old,' implies nostalgia and reflection over time's influence on youthful innocence and optimism.