What if you got a time machine to travel to the past!!!
Everybody wants to change things or change present life and think of past that it would be great if I have done this or that, if I would have taken that decision I would be somewhere else today etc etc. Everybody wants to change something from past. What will you do if you traveled to past?
If that would be possible then, I would undo whatever mistakes I had made in the past. I would stop people from doing wrong things that going to be a big change in their life.