From the benefits of fear is that it controls the desires and lessens the pleasures.
Therefore a person will hate a sin that he used to love, just as a person who desires honey would hate it if he knew there was some poison in it. Thus, desires are burned by fear, and the limbs are restricted (by this fear), and the heart becomes humble and submits. Arrogance, hatred, and jealousy leave him.
His main focus and worry becomes his fear, and looking at the seriousness of his destination. He has no time for anything else, and no concern except to take himself to account and watch his deeds.
He is stingy with each breath and each moment, and he accounts for every one of his thoughts, footsteps, or words. His situation is like that of one who fell into the claws of a predatory animal, and he does not know if it will become heedless of him so he can escape, or if it will attack him and devour him.
Such a person would have no other concern but that - so the strength of a person's monitoring and taking account of himself would be according to his level of fear.
While the level of fear would be according to his knowledge of the greatness of Allah and His Attributes, and his own personal faults, and (knowing) what lies ahead of him of dangers and horrors.
The lowest level of fear that shows its effect upon a person's action is what prevents from performing forbidden deeds. If he stays away from what could lead to something forbidden, it is called Wara’.²
Ranks Of The Fearful P.20-21 By Ibn Qudāmah al-Maqdīsī | Published by Dār as-Sunnah Publishers