Musar על משלי 28:14

He said after this (Proverbs 28:14), "Happy is the man who is always afraid, but he who raises his heart falls into misfortune." [Its] explanation is, even though he "confesses and gives them up," he should always be afraid [that] maybe he has not filled the [required] measure of repentance. For it requires many levels, so he should increase his fortitude every day to attain [these] levels. He should also be afraid [that] maybe his impulse will return to him. So he should guard against it every instant, always add fear of God to his soul and always pray to God to help him towards repentance and to save him from his impulse. "But he who raises his heart falls into misfortune": One who says in his heart, "I have filled my measure of repentance," and does not always make efforts to acquire [higher] levels of repentance and to add fear to his soul will be punished for this. For he is of a raised heart and does not recognize the deficiency of his spirit. And if he does not recognize the greatness of his obligation to refine his ways with great refinement, he will also not guard himself from his impulse, which always ambushes him. Hence he will fall into the hands of his impulse.

Of these two dispositions the sage saith (Prov. xxviii. 14), "Happy is the man that feareth always; but he that hardeneth his heart shall fall into mischief." But as regards the great men who are mentioned as possessors of this quality, heavenly signs gave evidence of their possessing this power, thus Joshua, Gideon, Samson, Saul, David, Jonathan, Joab, and Abner, and others like them, whose power gave evidence of the quality of valor, were praised therefor; and those whose weakness, in contradistinction to the former, gave evidence of the quality of cowardice, were not commended for it, as I will show in regard to them in the following chapter.

Therefore, they will choose only to maximize these means and to be stringent in all of their details, finding no rest or peace due to worry lest they possibly lack what will bring them to the perfection that they desire. This is what King Shlomo, peace be unto him, said: "fortunate is the man that fears always" (Mishlei 28:14), which our Sages explained (Berachot 60a) refers to matters of Torah.