Over the years, there have been a slew of time travel movies. Each have tried to put a different spin on the method of time travel, but most have basically still boiled down to three basic methods. One is the idea that, no matter what you do, you cannot change time. Think you're going to go back in time and kill your grandfather so you won't be born? Looking over the fact that you're kind of a douche for killing your grandfather, in this concept of time travel, your actions will be worthless. It's not that time is so much self-healing as it is that you're not quite as clever as time. The thing you think you changed never happened and whatever it was you did to change it made the very thing you didn't want to happen, well, happen.