年少不知精子贵老来望逼空叹息
[nián shăo bù zhī jīng zi guì lăo lái wàng bī kōng tàn xī]
It refers to a traditional view implying young people may waste their energy and not cherish opportunities or health ('precious essence'), then regret as they age - although note this phrase mixes modern vernacular into a traditional concept rather humorously.