Don't count your chickens before the eggs have hatched
别过早乐观，不要依赖尚未实现的事情做计划，避免失望。
劝人谨慎，避免过度乐观或提前庆祝。
例句
You might win the lottery, but don't count your chickens before they hatch.
典故来源
源自伊索寓言《挤奶女工》，女工幻想卖鸡蛋发财却打碎篮子，警示空想。