“How can one be on guard from what he does not know to be on guard from?”
He who does not know Fitan; and does not know its effects, outcomes, and customs perhaps he will fall into some of it and be stained with it, and it harms his life; then after that what reached him of regret overtakes him.
Knowing the effects of Fitan serves as a great benefit for the servant, and is useful to him as a tremendous benefit because it is from examining outcomes and consequences of matters.
This is considered to be from the servant’s sound judgment - meaning, that before he gives priority to a matter he examines its outcome and effects.