I once leased a very expensive software product and then abandoned it because our operation wasn’t in a position to integrate it in a productive way.
It still makes me mad that I paid THOUSANDS of dollars for a software product that was never put to use, but I couldn’t afford to waste more time and money trying to make a square peg fit in a round hole.
It was a costly failure that left me with two choices:
Rehearse the failure as a sort of punishment for my bad judgement or
Interrogate that failure for anything it could teach me about how to make better choices moving forward It probably seems painfully obvious which path is more profitable, but there’s a decent chance you’ve chosen option 1 a time or two in the life of your business.
There is no CTRL-Z. You can review your mistakes, but you can’t revise them. 
You only have what’s next.
Instead of reliving your least favorite decisions as a way of reminding yourself of your fallibility, what if you interrogated your mistakes by asking…

What can that experience teach me about myself, my business, the market, etc.?
How can that experience have a positive influence on what I am doing now/next?
And ultimately, can I find space for gratitude?
There is no going back, only pressing forward.