don't count your chickens before they are hatched.”意思是“鸡蛋未孵出，先别数小鸡。”引申意为“别高兴地太早、不要过早打如意算盘。”

【例句】
Don’t count your chickens before they hatch. I think we need to make further contact with them dispelling all their misgivings.
不要高兴得太早。我觉得有必要进一步与客户沟通，消除他们所有的顾虑。

It's quite possible that you will get the job, but don't count your chickens before they are hatched.
你很有可能得到这工作,但也别过早乐观.