Hindsight is 20/20. . .

Packer from the U.S. Forest Service Northern Region 

but at some point, that doesn't really do you much good.

And for that matter, it isn't really 20/20.

Human beings prognostic abilities are notorious poor, in spite of what we like to think.  We're really good at recognizing patterns, but it's been established that we see patterns in things that aren't actually there.

Added to that, while hindsight may be 20/20, immediate hindsight and distant hindsight aren't the same thing.  It's one thing to look at a recent mistake and conclude, well that was a mistake, or to look at something that was a success and realize that.  But mistakes in particular often don't really set in as to their full magnitude, if at all, for a long time.  By the time that hindsight snaps into focus, it may truly be difficult, or indeed too late, to do anything about them.

Which gives us that old adage about not looking back, which gives us such quotes as this from Churchill

What is done, is done. Learn from it and always look forward. Every day is a new opportunity to grow, to learn and be better than we were yesterday.

That's probably the best view, but it's not always the easiest one to take.