It pays to learn from yesterday’s mistakes. If you can’t wind back the clock to correct your wrongs, then why not learn from it.
There is nothing to be gained by lamenting over what you cannot change. The question now is what can you do to avoid making the same mistake again. That is the lesson. Apart from learning from your mistake, you also are in a better position to advise or correct other people who are doing what has already caused you some heartache.
Some mistakes are a blessing in disguise because the error might have occurred at a time when your loss was minimal. At least you now have a chance to catch up. If that mistake had occurred when there was a lot more at stake, then the journey back to normalcy would be a lot harder.