النحو في الكلام كالملح في الطعام
Grammar in speech is like salt in food.
If the point is stated as “a little improves it, too much ruins it,” a difficulty arises: quantity is clearly applicable to salt, but treating correct grammatical rules as useful only in a small dose and damaging in a larger one is misleading.
A more defensible reading is proper application: observing the relevant requirements makes speech or food fit its purpose; neglecting what is needed may spoil the outcome. The proposed point of likeness must apply intelligibly to both sides.