Reading
Time is precious(珍贵的).Nobody can afford to waste time.Once time has gone by,it wiil never return.You can never turn the clock back.Time passes very quickly.In fact,people say time flies.Time and tide wait for no man.We should,therefore,make the best use of our time.
can afford to + 动词原形
can afford +名词 负担的起
turn the clock back 将时钟倒转
Time and tide wait for no man 岁月不待人
make the best use of 充分利用
Grammar Points
unless if once when after 从句为一般现在时或现在完成时，主句与will（表将来）can （表能力）may（表许可）等连用
Unless I have extra money,I won't buy it.
if he works hard,he'll get somewhere.
when I have earned enough money,I can travel with you
