Kaisipang Hudyo sa Mga Awit 51:5: Duties, Derashot HaRan & Guide for the Perplexed

(1) The penitent must understand clearly that he did a disgraceful act. Because, if this is not clear to him, and he is in doubt or ignorant of it, it is not possible for him to regret it and seek forgiveness for it, as written: "For I know my transgressions, and my sin is ever before me" (Tehilim 51:5)

(2) That he recalls them always, and places them before him, opposite his face, as written "For I know my transgressions, and my sin is ever before me" (Tehilim 51:5).

The answer to our question, then, [as to how one can repent if he cannot fulfill the requirement of "the same age period"] is that his repentance, indeed, does not increase his merits, but it suffices to atone his previous transgressions. However, this repentance must also be complete. It is not enough that one say "But we have sinned and been guilty" with his mouth and lips and not constantly search out his deeds. But all men must always examine their ways, both in respect to the transgressions between man and G-d and those between man and his neighbor, and their transgressions must be constantly before their eyes. For we see our righteous anointed one [David] to have said (Psalms 51:5): "For I know my offenses and my sin is constantly before me" — in spite of our sages' having said (Shabbath 55b): "All who say that David sinned are mistaken." Notwithstanding this, because there was some inadvertent element of sin, he placed it constantly before his eyes and was worried and afflicted by it, as it is written (Psalms 38:19): "For I will declare my transgression; I will worry over my sin" — though he did not commit the ostensible sin and though "all who say that David sinned are mistaken."