Hormones influencing the sensitivity of the person to environmental stimuli.

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.)

Digestion is quickly shut down during stress…The parasympathetic nervous system, perfect for all that calm, vegetative physiology, normally mediates the actions of digestion. Along comes stress: turn off parasympathetic, turn on the sympathetic, and forget about digestion.

Give lab rats oxytocin and, according to that meme, they get better at talking about their feelings and sing like Joan Baez.

What does the frontal cortex do? Gratification postponement, executive function, long-term planning, and impulse control. Basically, it makes you do the harder thing.

As long as experiencing your optimal level of good stress doesn't damage others, it's hard to objectively define where normal enjoyment of stimulation becomes adrenaline junkiehood.

Only humans invent moralizing gods who monitor our behavior.