A person cannot remember all his bad conduct from the day he was born and we cannot say that the Holy One Blessed be He doesn’t accept his prayers until he confesses and repents of all his transgression. If he details and regrets all the sins that he can remember while meditating to include and repent on all other sins from his past then he gets cleansed.
It’s like the removal of Chametz before Pesach. We check and remove all that we can see and meditate that whatever Chametz that we couldn’t find is cancelled together with what we found.
“וְאִם פָּרוֹחַ תִּפְרַח הַצָּרַעַת בָּעוֹר וְכִסְּתָה הַצָּרַעַת אֵת כָּל עוֹר הַנֶּגַע מֵרֹאשׁוֹ וְעַד רַגְלָיו לְכָל מַרְאֵה עֵינֵי הַכֹּהֵן.”
“But if the skin disease breaks out all over his skin so that it covers all the skin of the infected person from head to foot, as far as the priest can see,”
We learn from this verse that the process of ‘examination’ of the infected, is ‘as far as the priest can see’. Whatever the priest could see in one scan of the infected person is sufficient to determine the state of the entire body.
King David portrayed himself as Chassid because he confessed his sins, cleaned himself and was holding fast to the Right, Chessed.
Before we go to sleep and being judged in the upper court for our actions during the day, we use the prayer of King David (Psalms 51) to support our confession before we go to sleep. It cleanses our soul and guarantees us a clear path to higher spiritual levels and better sleep to receive greater energy for the coming day.
Read Psalms 51