dont count your chickens before theyre hatched

Dont count your chickens before theyre hatched is an idiom which means that you should not count on something before it happens or expect your hopes to be fulfilled. This is basically a cliche which is advising you to not count on anything because at any point, something could go wrong and it may not work out. For instance, counting on money to be coming in when it isnt guaranteed can cause you more worry in the long run in the case it does not come when you expect it.