First of all, figure out what went wrong and caused the breakup in the first place. Pinpoint when your relationship took a wrong turn and went downhill from there. Although you might wish you could go back in time and undo your mistakes, that's not possible, so all you can do is learn from them and move on.
When you understand what happened and what you did wrong, you look at your relationship in a whole new light. The change in you is an important step in getting ex back. When you are wondering how to win your ex back, it is important they see that you fully understand what you did wrong and didn't just push it aside.