Kill the goose that lays the golden egg/eggs
Definition 1 of 1
Pro Tip 1/3Aesop's Fable
The phrase originates from a fable by Aesop about a farmer who sacrificed long-term benefits for short-term gains. 
She's risking the project's future if she cuts corners; it's like killing the goose that lays the golden eggs.
Pro Tip 2/3Idiomatic caution
Used to caution against actions that could ruin something that’s consistently beneficial. 
Don't overwork your staff, or you'll kill the goose that lays the golden egg.
Pro Tip 3/3Metaphoric value
This metaphor is often applied to financial and business situations, but can also relate to personal relationships. 
Ignoring her health issues might kill the goose that lays the golden egg.