I agree with user 130057 on this one.
It is a persons past, good parts and bad, which make that person who they are. Mistakes and the consequences we suffer for them, are what make us grow as people. If mistakes could be written off by turning back the clock then we would learn nothing. Besides, it would be all too easy to erase all pain from your life, and without pain, we are unable to fully appreciate the joy and pleasure in life.