Watched this movie for the three times today, and I'm still attracted and impressed by the idea and the plot.
When the old time is fixed and unchangeable, the present is fixed, all one can do is to accept it. There is no other choice. But as Evan finds out his talent, the story just speeds up. He tends to go back to the old time to "fix" everything, rather than accept it. His "sense of reality" has actually disappeared. When he is put into the jail, all he wants to do is reading his diary to get out from that "reality".
Sometimes we say should've, could've, would've, but I never regret every step I took, because they make me who I am, and I am satisfied with myself. I can't change the past. But if I could, I won't.