My teacher was making a joke about an idiot would be a lot happier according to the definition of reason. In a sence Kant agrees with another philospoher, David Hume. Hume believed passion was going to bring man morality, and that reason is only the comparing of ideas, and that reason will influence us away from our passions. So Kant too says that reason influences our will. So-if the cultivation of reason is required for the purpose, and the purpose leads to happiness.
Reason is infact compatible with happiness.
I don't know, maybe this will only help with the questioning you can give to someone else, perhaps another philosophy teacher. I also found Encycolpedias of philosophy very helpful as i was looking for a better understanding of other philosophers. I am studying Kant in my philosophy class. I am a freshman in college and I am thoroughly confused by his Critique of Pure Reason. Instincts can get you closer to what you want to accomplish.