Barry: I don't understand. I thought that I was helping people by stopping Mardon.
Harrison: Yes, but this new ability of yours, Barry, is dangerous and you only traveled back in time one time. What if you traveled back in time decades, centuries? Imagine the havoc you could wreak.
Barry: But I will have the opportunity to travel back in time in the near future to save my mom. Are you saying I shouldn't?
Harrison: I'm saying how many more people could die if your mother lives.