This is not my own mistake, but during Trig class I used to sit beside this guy who would try to copy everything from me. Sometimes I let him, other times I didn’t. My teacher was really lazy and never monitored us during a test, so he would always get away.
This one time we had a test. I was too tired to fight him about copying, so I just let him be. And he copied my entire exam. All of it. Including MY NAME. In the end he didn't have a score and got a zero. Thats karma for you