What I was familiar with was parents who were very strict and perfectionistic, and for whom very few things were ever good enough.

I think both parenting and your peers play a big role in it. But I do also believe in life changing events.

My mom is Chinese and always compared me to the best in the class. My Dad believes that in some case the time spend bringing something from a 7 to a 9 can sometimes be spend the improve somewhere else. So, I got the best (or the worst) from both sides. I went from an extreme pessimist at the age 15 to an extreme optimist at age 25, and I don't know where the change came from, but I often think it is because I became good at something I loved.