let (the) best be the enemy of (the) good

To allow the demand, desire, or insistence for perfection to decrease the chances of obtaining a good or favorable result in the end. (Usually used as an imperative in negative constructions.) I know you want your research paper to be flawless, but don't let best be the enemy of good, or you won't even finish it in time! As a manager, you have to realize both the potential and the limits of your employees, so be sure not to let the best be the enemy of the good.