1. Going back in time can't change history, because going back in time will change all relevant historical events because of the events you changed, and then change you today, so that the events that you change history now won't happen. This is the so-called grandmother paradox.

Instead of thinking about changing yourself from a certain point in the past, it is better to change yourself from now on. There will always be some regrets in our life. There is no perfect life, so is anyone.

We don't have to go back. As long as we do well in the present, we can also change history.