NOTHING I would change nothing. Bad shit happens to good people, things don't go to plan, but that is life my friends. Everything happens for a reason and although hindsight is a great thing, worrying about the past, hoping you'd turned left instead of right or gone up when you should have gone down, helps us make sense of things today, there is nothing we can do!! Embrace the decisions you make, learn from them, the good ones and the bad ones.
You are who you are because of the things that have happened to you and the decisions made.