''(aka "Counting ''your'' chickens before they hatch")''

Sometimes, managers will make commitments to their boss based on uncertain outcomes--this is the nature of forecasting.  In some cases, however, such estimates will make overly-optimistic predictions about the future -- depending on an outcome (a project, etc.) with a low chance of success. In many cases, the manager's subordinates are then expected to expend extra (and often heroic) effort in order to ensure that the project/whatever ''does'' succeed.

Like the Aesop fable, this is counting the chickens before they hatch. And like in Aesop's fable, it's not a good idea.
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CategoryIdiom