He who tries to keep a foot in one boat and the other foot in another will end up getting nothing done. (Such a person must be too ambitious, "biting off more than he can chew.")
Water spilled on the ground can never be collected; mistakes, once made, can always be rectified.
(All that's happened before is "water under the bridge.")
Happiness and sweat are brothers; luck and hard work are a family. (Industriousness and the fortune that come from it cannot be divorced from each other; one definitely leads to the other.)
The more you sharpen a knife, the quicker it cuts; the more you use your brain, the faster it thinks. (The brain works if one would only use it.)
For each day an evil man lives, the decent common people must suffer for a year. (The evil of one bad person spreads like a cancer.)
The loudest bird is not necessarily the biggest. (Looks may be deceiving. "All that glitters is not gold.")
You wouldn't ask a monkey to collect fruit anymore than you would tell an otter to watch over the fish. (Taiwanese would say, "Don't send a ghost to the pharmacy to fill a prescription." Trying to cut corners while doing something important can lead to disaster.)
Sticking your hand out won't block the wind, and pulling your ears close to your head won't keep you dry from the rain. (To engage in pointless, useless activities, tasks that are doomed to failure from the start. Mandarin speakers would say "to look up a tree for a fish." Japanese speakers would say "to look for oysters in a field.")
Wood not drilled cannot be connected with other wood; a person not taught remains ignorant. (Like so many other proverbs, this rhymes in Chinese. Think of learning as akin to drilling, with information, wisdom, etc., being drilled into the brain so that one may become learned, better connected to the world around him/her, and disabused of his/her innate ignorance.)
Just as loud thunder usually means only a little rain, an arrogant loudmouth is usually one with only a few accomplishments. (Some people are all talk. "Talk is cheap.")
(1) Yanhai Langhua, Zhang Dingya, et al. (2) Zhongguo minzu minjian wenxue (Folk literature of the peoples of China). Zhongyang minzu xueyuan xiaoshu minzu wenxue yishu yanjiusuo. Beijing: Zhongyang minzu xueyuan, 1987.