When we get angry or frustrated with someone, it’s because of something they did (or didn’t do) – in the past. Likewise, if we feel shame, regret, or guilt – it, too, is based on something from our past.
In fact, nearly all of our judgment is based on the past. But the past is gone. It’s over. It doesn’t exist. Yet we often cling to it as if it were real.
Consider this line from A Course in Miracles: “God knows you now.” In other words, our only reality is the present moment. There are no sins we (or others) have committed that require any sort of atonement.
The regret or anger over the past and worry about the future are purely ego mechanisms to keep us away from the only reality that exists – now.