Because we always have with us our flesh that has been corrupted by original sin, and we sin in many ways every day and deserve nothing but punishment, we therefore constantly need the comfort of forgiveness. Just as we pray for daily bread every day, so we also need to pray for spiritual bread or forgiveness of sins every day.
Gen. 32:10: I am not worthy of the least of all the mercies, and of all the truth, which Thou hast showed unto They servant.
Luke 15:21: Father, I have sinned against Heaven, and in they sight, and am no more worthy to be called thy son.
Dan. 6:10,11: He kneeled upon his knees three times a day, and prayed, and gave thanks before his God, as he did aforetime.
Dan. 9:18-19: We do not present our supplications before Thee for our righteousnesses, but for Thy great mercies. O Lord, hear; O Lord, forgive.