I first became a vegetarian when I was nine, in response to an argument made by a radical babysitter. My great change - which lasted a couple of weeks - was based on the very simple instinct that it's wrong to kill animals for food.
I didn't go to classes there, but ended up at the Cinematheque, and there it opened up even wider because there I saw a variety of films from all over the world.
I still have a lot of those depressive thoughts, but now I have the foresight to tell myself, 'Don't think like that,' and things seem better.