Life revolves. You cannot go back one minute, or one day. In light of this, there is no use marking time in any one position. Life will continue without you, will pass you by, leaving you hopelessly out of step with events. That's why you must engage life and maintain your pace. Don't look back, and don't step back. Each time you make a decision, move forward.While I agree that we should always look forward, we do have the same problem with the future as we do with the past. While we can't re-engage what has been, we concurrently can't engage what is not yet. All we CAN do is deal with the present moment -- the right here in the right now.
~ from 365 Tao: Daily Meditations, Entry 149 ~
That said, Ming-Dao does offer us a salient point. If we don't keep our eyes on where we're headed, it's next too impossible to stay on course.
Have you ever tried walking forward for any distance while looking behind you? If it's anything more than a quick glance, you're bound to step in a hole or run into a person or object. If you continually look over your shoulder on a busy downtown street, you run a great risk of being run over!!
There is nothing wrong with examining one's past in order to glean wisdom from our experiences. However, wallowing in what could have been but isn't will not change one damn thing. Once we screw up, it's over and done with. No amount of hand wringing can change what has already been wrought.
Beating yourself up for what you cannot change is a selfish waste of time and energy. It also sets the stage for you to make the same mistake all over again because you refuse to focus on what's right in front of you.