A Squirrel
When you mess up your own plan because you're too dumb to know what you're doing.
I was trying to finish my homework, but I spent 2 hours watching cat videos. What's wrong with me?
I had a perfect plan to get rich, and I lost all my money because I bet on a squirrel to win a race.
I started a fire to keep warm, and now my house is on fire. I'm a dumbass.