I would change nothing.
Though my past is tough, and stretches the word miserable, I would never change anything that happened.
For every mistake one makes, a lesson is learned. You learn about life, about people, and especially about yourself when you make mistakes..
I think of screw-ups as an opportunity more than a burden.. You can learn various things from them.
What not to do, and what to do next time.. They are your teachers, so watch and listen closely.
Besides, when things are harsh you slowly toughen up as time goes on, and usually are more ready for what life throws at you than others.