crystallized intelligence. This is defined as the ability to use a stock of knowledge learned in the past.

And that means not trying fruitlessly to get ahead on a speeding treadmill by falling over and over again for marketing gimmicks. It means turning the treadmill off by managing our wants. In the words of the Spanish Catholic saint Josemaría Escrivá, “He has most who needs least. Don’t create needs for yourself.”[19]

You can finally relax

You seek the worldly rewards of success, you achieve some (or a lot) of them, and you may be deeply attached to these rewards. But you must be prepared to walk away from these achievements and rewards before you feel ready. The decline in your fluid intelligence is a sign that it is time not to rage, which just doubles down on your unsatisfying att

Many success addicts confess that they feel like losers when they see someone else who is yet more successful. Success is fundamentally positional, meaning it enhances our position in social hierarchies. Social scientists for decades have shown that positional goods do not bring happiness.

Yet we still have the urge to acquire more to get good feelings and to signal our success to others, and to avoid less to avoid bad feelings like fear and shame.

A big, strong prefrontal cortex makes it possible for you to get better and better at your specialty, whether it is making a legal case, doing surgery, or driving a bus. In middle age, the prefrontal cortex degrades in effectiveness, and this has several implications. The first is that rapid analysis and creative innovation will suffer—just what we

Devote the back half of your life to serving others with your wisdom. Get old sharing the things you believe are most important. Excellence is always its own reward, and this is how you can be most excellent as you age.

And thus, the Harvard Study of Adult Development was born. The original cohort of 268 men included people from many walks of life, including some who went on to become well-known, such as John F. Kennedy and Washington Post editor Ben Bradlee. Still, over the decades it was deemed too demographically insular—all Harvard men!—to give generalizable r