Mistakes are inevitable part of our lives. If everyone could lead a happy life just by learning from others mistakes or experiences. The journey of OUR life would not have been called an experience by itself. Regretting over past decisions can only hinder you from experiencing today's happiness. Instead take learnings from those mistakes. Certain situations or conditions created from our own mistakes can be irreversible, instead of getting bogged down and hovering over the same thing. Try to accept and make peace with it. Lead a happier life. Well! It's for you to interpret rightly which things can be accepted in life and which should ones should not be tolerated and be corrected.