I Wish I Wish I Hadn't Sat On That Fish
For anyone unfamiliar with The Simpsons, the title is taken from an episode when Homer travels back in time. He sits on (and kills) a fish, which leads to a chain reaction of death and destruction.
When I observe the consequences of bad descisions unfolding in my life, I always think of that quote. Most of the time there seems little more to be said.