Complex sentence: The meaning of "The perfect is the enemy of the good" is that one might never complete a task if one has decided not to stop until it is perfect: completing the project well is made impossible by striving to complete it perfectly.
Split into simpler sentences: The meaning of "The perfect is the enemy of the good" is that we might never complete a task if we have decided not to stop until it is perfect. In that sense, completing the project well ("the good") is made impossible by striving to complete it perfectly.