Remorse is a complicated thing and it is made-up of so many components that blur the mind to the past and the present. We become confused between "what was done that cannot be changed" and "what is not yet done".
The cups are already swept away by the currents. One cannot go back; to dwell in the past is futile when we are at the present. Pining away for what we lost blinds us to what we have.
