It is said, ‘I have carried away your transgressions like a thick cloud, and your sins as a mist’ (Isaiah 44:22).
The pardoning of sins is not like removing a stain, which leaves a faint mark, but like a wind dispersing the clouds, leaving no sign of their having been there before.
Forgiveness becomes, then, the actual creation of a new temporal order in which it is as if the sin never existed.
Moreover, it is as though by the very power of repentance ‘sins have become merits’ (Yoma 86b), and the past is a rewritten according to another scale of values.
–Rabbi Adin Steinsaltz
From “Days of Awe”, in A Guide To Jewish Prayer, p. 195-196, by Rabbi Adin Steinsaltz