511. Now or never.

机不可失，失不再来。

512. Old birds are not caught with new nests.

新巢捉不到老鸟。

513. Old birds are not to be caught with shaft.

老谋是不会失策的。

514. Old love will not be forgotten.

旧情永难忘。

515. Old vessels must leak.

旧船必漏。

516. Patience is a virtue.

忍耐是一种美德。

517. Patience is bitter, but its fruit is sweet.

忍受是苦痛的，但它的果实是甜美的。

518. Patience is the best remedy (or medicine).

忍耐是最好的药物。

519. Penny wise and pound foolish.

小事聪慧，大事糊涂。

520. People do not lack strength; they lack will.

人们不缺力气，缺的是信心。