Well, I could be wrong, but I think the topic implies the action, the event that you did wrong and would like to do differently, if given a chance. Describe the event, why and how you would like to change or redo it.
"if I had a second chance to do something over I'd stop worrying about what people think.
It is within your capability to change something in your character, that is to stop worrying about people' thoughts, so you can start even now. You do not need a second chance.