Then I thought about the practicality. If you're permanently disabled in some way in the future and you go back to have a healthy body and avoid the injury, that alone is worth the effort. Going back to change specific minor events in your life is hardly worth it unless you're getting Groundhog Day-like repeat attempts until you're satisfied with the result. In most of the scenarios I imagine, I would go back to particular days when I was between 5 and 12 years old. Then I thought about some of the things I would have to decide on. The first and most difficult is - which girl you met in your entire life that you "missed" the first time would you choose to go after the second time, knowing how you screwed it up once - assuming you've even met them the first time around. Do I choose someone I knew in school? No offense to anyone, but most of them turned out fairly average and very few would be someone I would want to date now. The next most obvious choices would be famous people now. I thought about Japanese and Korean pop singers specifically because I was listening to that at the time, but you could fill this in with any example. Most of the ones I listen to are around 20 years old now - at the ages I would want to go back to, many would even be born yet! Would you really want to wait as much as 20 years for them to be old enough to go after? Would you want to spend a lot of your gambling and stock market gained resources arranging for you to be able to meet them at the right timing? In many of my cases, I would have to arrange it so they would never become a celebrity to begin with. Would that change events in their life in general enough that they wouldn't be like the version you remember and still someone you would be interested in?
Basically, I've come to the conclusion that, other than to prevent or recover from serious injury, I would probably not want to redo much (other than starting college at a normal time after high school, finishing a degree quickly, and actually playing sports through college, and probably end up as a professional player or get into the pro wrestling industry much sooner and at a much more booming time.) Instead of redoing events and potentially using up another 20 years to meet or re-meet someone specific and potentially screwing it up again, I think I would be better off putting effort into improving my chances of "positive events" moving forward more than I currently do, so I'm in the right place at the right time the first time around.