I am in agreement that what happens to us builds character as to who we are. And, sure, I've taken many missteps -- some which I truly regret -- but my aim has always been "do no harm to others" and the damage of what I've instituted has been to myself, and I can live with that. Wish I could lay the same claim unto others in my family who regularly have resorted to treachery. (shudder)
In order to break the pattern, you have to break the mold. Which means actively seeking that which is different. When you come from a horrific situation, if you're open-minded, you can appreciate things so much more. We tend to take a lot of things, good and bad, for granted. But experiencing both ends of the bell curve lets you make better choices and have a better understanding of what you will and won't tolerate.
I think it was Maya Angelou who said so wisely "When someone shows you their true colors once believe them." Unfortunately for me it has taken the full three strikes before the boundaries are set and they're officially out....or at least maintained at a safe far distance for family.