A good medicine tastes bitter.

良药苦口.

A young idler, an old beggar.

少壮不努力,老大徒伤悲.

Adversity reveals genius, fortune conceals it.

苦难显才华,好运藏天知.或：逆境显示天才，幸运掩盖天才。

A stitch in time saves nine.

防微杜渐。及时缝上一针可免将来缝九针。小洞不补，大洞吃苦。

All for one, one for all.

我为人人,人人为我。人人为一，人人为一。