Good Game Theorist

Today I learned a lesson in my game theory class. Being a good person and a good game theorist don't usually line up. We played a game where you and a random person in the class were competing for extra points on the midterm and didn't know what the other person was going to do. I chose action y which would benefit both of us equally. The other person, however, chose action z which was purely in their own self interest. It left me with zero points and them with 6. That is what can happen when you try to be a generous person in game theory, you get burned.