don't plan your future according to events that may or may not take place, don't depend on something whose outcome is uncertain, do not count on things too soon particularly if you don't have them yet
DON'T COUNT YOUR CHICKENS BEFORE THEY HATCH
Meaning of DON'T COUNT YOUR CHICKENS BEFORE THEY HATCH in English
Explanatory English dictionary bed edition. Толковый словарь английского языка Редакция bed. 2012