Hardwiring Happiness: The Practical Science of Reshaping Your Brain—and Your Life

This is a problem because the hippocampus helps you put things in perspective while also calming down your amygdala and telling your hypothalamus to quit calling for stress hormones.29

Over time, negative experiences make the amygdala even more sensitive to the negative. This snowballing effect occurs because the cortisol that the amygdala signals the hypothalamus to call for enters the bloodstream and flows into your brain, where it stimulates and strengthens the amygdala.

Unlike fleeting mental states, inner strengths are stable traits, an enduring source of well-being, wise and effective action, and contributions to others.

intense, prolonged, or repeated mental/neural activity—especially if it is conscious—will leave an enduring imprint in neural structure,

As they say in neuroscience: Neurons that fire together wire together. Mental states become neural traits.

Because they lived in small bands, it was uncommon for them to meet people they didn’t know, and often dangerous when they did. While some bands interacted peacefully with each other, on average about one in eight men died in conflicts between bands, compared to one in a hundred men who died due to warfare in the twentieth century.

Our ancestors could make two kinds of mistakes: (1) thinking there was a tiger in the bushes when there wasn’t one, and (2) thinking there was no tiger in the bushes when there actually was one. The cost of the first mistake was needless anxiety, while the cost of the second one was death.

Whatever we repeatedly sense and feel and want and think is slowly but surely sculpting neural structure.

If you don’t make use of this power yourself, other forces will shape your brain for you,