Xué rú bùjí, yóu kǒng shī zhī.
学如不及，犹恐失之。
Learn as if you are always left behind, and fear you may lose the knowledge after you grasp it.
学 learn, study;
如 as, like;
不 no, not;
及 reach, come up to;
犹just as, as if;
恐 fear, terrify;
失 lose, miss;
之 this