You can only make things worse

You need to amass one kilogram of your own feces in a ceremonial bag for the power to take effect.

Applies only to non terrestrial events

You can only make small changes, and it doesn't always work. So, you don't actually know if you have the power or if something slightly improbable happened.

You go forward in time to a point where the changes no longer matter.

The probability of gaining or losing a genetic trait in your body also changes based on the probability change you make