He who controls the past controls the future.
The past has no power to stop you from being present now. Only your grievance about the past can do that. What is grievance? The baggage of old thought and emotion.
. . . the mind is desperate to fix the river {of events} in place: Possessed by ideas of the past, preoccupied with images of the future, it overlooks the plain truth of the moment.
The wise man looks back into the past, and does not grieve over what is far off, nor rejoice over what is near; for he knows that time is without end.