From a little spark may burst a mighty flame.

星星之火可以燎原。

You cannot burn the candle at both ends

蜡烛不能两头点,精力不可过分耗

How sharper than a serpent's tooth is to have a thankless child. 

逆子无情甚于蛇蝎。

Miracles sometimes occur, but one has to work terribly for them

奇迹有时候是会发生的,但是你得为之拼命的努力。

A young idler, an old beggar. 

少壮不努力,老大徒伤悲

这句谚语字面意思是,小时候游手好闲老了只有当乞丐的份了,就是我说中国人说的“少壮不努力,老大徒伤悲”。idler(n.)懒汉,无所事事的人。