I chose to be a vegetarian at 5. I was an animal rights activist back then.
I think my turning point was when I went to a farm at 5 and was peer pressured into milking a cow. I had to squeeze it's utter and it was traumatizing. As I squeezed the cows utter, it let out the most depressing moo. I knew that cows struggle just from that simple moo. Literally gave me Skyscraper teas "You can take everything I have, you can take everything I am, like I'm made of glass, like I'm made of paper"
So first I gave up milk, then soon after meat. I'm almost 20 and haven't looked back since.