There are so many quotable points of the Course in Miracles text that cuts through the daily life bullshit and tells it like it is. "The one wholly true thought one can hold about the past is that it is not here." A powerful statement that rings very true to me.
Think about it. Its a fact that the past is not here and there isn't anything you can do about it. The course wanted that this lesson "can be done four or five times during the day, unless you find it irritates you." It does irritate me, because I was irritated at how much time my mind wastes thinking about the past. I thought I was pretty good about living in the present moment!
I think the past is sometimes good for review to determine any lessons to be taken from the past experiences. But woulda/coulda/shoulda and replaying past scenarios over and over - it is an unproductive way to spend your time and it does nothing to help your present situation.
I did take solace in the fact that awareness of a problem is the first step to changing it. And I was supported with the lesson text that said "...understanding will finally come to lighten every corner of the mind that has been cleared of the debris that darkens it."
Debris. That is a good word to describe all the past thought-form junk floating around in my mind. So that makes me a metaphysical garbage man on a cleanup mission.