For You are He Who remembers forever all forgotten things -- Rosh Hashanah Musaf Amidah.
Question: How does this Divine attribute, remembering all that is forgotten, work in our favor?
Answer: There are many good things that a person does without making any issue of them. Since he has long forgotten about them, when the Day of Judgment arrives, he does not make mention of them as merit for his deserving to be blessed with a good year. Fortunately, G-d does not forget. Thus, we beseech Him, since You do not forget anything, take into consideration all the good things we have done and forgotten.
On the other hand, if one forgets about his sin and does not repent, G-d will remember it and hold him accountable. But if a person committed a transgression, and is remorseful and conducts himself, as King David said, in a way of "My sin is before me always"1 -- G-d will disregard this sin since He only remembers "what has been forgotten."2
