A Useless Time Machine

So I've invented time travel, but there's a problem with it, in that the universe is apparently self-correcting, and damn good at it.

See, like anyone, after the tests where I went back a few seconds, forward a few moments, I decided I wanted to stop millions of deaths, so I set the device to go back so I could kill just one person, you know who.

And then things went blurry, and the machine had reset. Any time I try to do something that is important, that act gets cancelled out.

So unless you really like stepping on butterflies...