Times, "Why Can Some Kids Handle Pressure While Others Fall Apart?" (my emphasis):
Like any kind of human behavior, our response to competitive pressure is
derived from a complex set of factors — how we were raised, our skills
and experience, the hormones that we marinated in as fetuses. There is
also a genetic component: One particular gene, referred to as the COMT
gene, could to a large degree explain why one child is more prone to be a
worrier, while another may be unflappable, or in the memorable phrasing
of David Goldman, a geneticist at the National Institutes of Health,
more of a warrior.
Or is it all just genetic?