If I could return to the past... I would do exactly what I did before.
If one day I had the chance to go back in time, I believe I would act no differently. That’s because the moment I revisit the past, the mindset would revert to that former day. The same perception leads to the same action.
The key issue wasn’t What I Did - it was How I Thought. My past-self made decisions based on my past-beliefs. So, the desire to alter the past comes from the fact that I’m using the present-day thinking to judge the past actions. THAT IS UNFAIR!
Want to rewrite the past? Start by editing the present! Because someday, this present moment will become the past of my future-self. In the same way, the future has been shaped by the way I fix the present. After all, this present is already the future life for my past-self. 
Let's practice mindfulness! By changing the present, I shape the future for my past-self, and alter the past for my future-self.
Change the present. Alter the past. Shape the future.