1、Everything has its time and that time must be watched.
万物皆有时，时来不可失。
2、Take time when time cometh,lest time steal away.
时来必须要趁时，不然时去无声息。
3、When an opportunity is neglected,it never comes back to you.
机不可失，时不再来;机会一过，永不再来。
4、Make hay while the sun shines.
晒草要趁太阳好。
5、Strike while the iron is hot.
趁热打铁。