Most people who do a lot of exercise, particularly in the form of competitive athletics, have unneurotic, extraverted, optimistic personalities to begin with. (Marathon runners are exceptions to this.)

Oxytocin is lauded for how it promotes warmth, generosity, social bonding, cooperation, trust, and compassion.

We are just another primate but a very confused, malleable one.

Until you appreciate something crucial - It is incredibly easy to manipulate us as to who counts as an Us, who as a Them.

We're getting along so well; I trust you so much for this one second that I'm going to let you yank on me.

We’ve evolved to be smart enough to make ourselves sick.

The gigantic challenge is the magnitude of the individual differences in the optimal set point for "good stress." For one person, it's doing something risky with your bishop in a chess game; for someone else, it's becoming a mercenary in Yemen.