shū dào yòng shí fāng hèn shǎo
书 到 用 时 方 恨 少
It is when you are using what you have learned from books that you wish you had read more.
解释 ( paraphrase )
读书到了要用的时候才悔恨读得太少。
这条谚语告诉我们:读书不多,到应用的时候就会感到知识不足。所以应该多读书,多积累知识。
This proverb reminds us that we can never read widely enough.
方:才。
Only, just when.
造句 ( example )
书到用时方恨少,什么都应该赶早学习,否则到了关键时候就会觉得后悔。