Three Big Takeaways:
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1. We gain more wisdom as we age. Wisdom comes from the accumulated set of things we've seen and experienced, our ability to detect patterns in those experiences, and our ability to predict future outcomes based on them. The more you've experienced, the more wisdom you are able to tap into.Young upstarts may be faster playing video games, but in the realm of wisdom they can't hold a candle to old-tiers who have been witness to so many things that seem to cycle around again and again. Wisdom enables you to handle some problems more quickly and effectively than the raw firepower of youth. (pg. 119)
    

2. Aging is an irreversible and inescapable process. But the effects of aging are reversible and subject to delay. There are many factors under our control - diet, social networks, sleep, visits to the doctor. But the single most important factor for vibrant mental and physical health is physical activity. This doesn't mean diet and sleep aren't important, and it doesn't mean if you engage in more physical activity you don't need to follow other healthy practices. What it does mean is you need to take physical activity seriously. (pg. 283)
    

3. Often we look at old age as a time of limitations and sadness. Of course, there are a lot of things we don't do as well as when we were younger. But that doesn't mean that all older adults are depressed. As a group, older people are actually happier than younger people. Happiness tends to decrease beginning in the late thirties (midlife crisis, anyone?) and then begins to increase sharply after age fifty-four. (pg. 370)
   
    

Other Key Ideas​​:
 

Older adults tend to be better at controlling impulses - they're better at self-control and self-discipline and tend to be better at rule-following than young adults. Self-control increases every decade after the age of twenty. Flexibility - your ability to easily adapt to changes in plans or to your environment - decreases steadily every decade after twenty. In addition, older adults are generally more concerned with making a good impression and with cooperating with others. Individuals become more self-content in old age. They are more self-contained, more laid-back, less driven toward productivity. Mood disorders, anxiety, and behavioral problems decrease past age sixty. (pg. 20)

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The number of times an event is repeated affects several aspects of memory performance - the ability to retrieve the event at a later time. The more times the event has been presented, the more accurate you'll be in recall and recognition, and the shorter will be the time it takes you to retrieve it from memory. The key to remembering things is to get involved in them actively. Passively learning something - such as listening to a lecture - is a sure way to forget it. Actively using information - generating and regenerating it - engages more areas of the brain than merely listening, and this is a sure way to remember it. (pg. 53)

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We need to fight against complacency and passive reception of new information. And we need to fight these with increasing vigilance every decade after sixty. Fortunately, there are things we can do to increase the durability and accuracy of memory. For short-term memory problems, training our attentional networks helps us to focus on what is going on right now and to store with clarity and increased precision the most important things we are thinking and sensing. This can be done by slowing down and practicing mindfulness - trying to single-task instead of multi-task - and being in the present. (pg. 56)

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The efficiency with which we learn new motor skills declines with age. We can learn well into our nineties, but the learning takes more concentration and more time. Older adults can learn how to use computers and cell phones, but they make more errors while they're learning and don't retain the new information as long as younger people. It's not that older adults are slower, it's' just that they are slower at adjusting to new things. If you are thinking there might be a correlation between this and the tendency for older adults to become more politically conservative - you might be onto something. (pg. 87)

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The most notable effect of aging is the decline in intellectual processing that some people undergo. But not all people. Some of us remain happy, healthy, and mentally fit while others start to lose it. What's going on in the brains of the older people who keep things going at high levels? Are they just barely hanging on or are they actually improving in some ways? I've come to believe that life after seventy-five can launch a period of intellectual growth, and not mere maintenance. Self-improvement and expertise are possible at any age, whether it's intellectual, physical, emotional, or spiritual. (pg. 115)

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People who retire fade rather fast unless they have something really important they want to do. It's feeling that you have purpose, and that you have less and less time to make your mark. Instead of slowing down you have to speed up. (pg. 135)

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Depression can affect people of any age, and it often goes undiagnosed in older adults. We may notice depressive-like behaviors in older adults and think it is normal aging. It is not. Depression is not occasional sadness, but persistent feelings of hopelessness, sadness, and emptiness that last for more than a couple of weeks. Signs of depression in older people often show up as lethargy, lack of motivation, and lack of energy rather than sadness. Older adults may not realize what they are suffering from is depression. The good news is that depression is less frequent among older adults than younger adults. (pg. 160)

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Insomnia, a hallmark for aging, is often an overlooked risk factor for late-life depression, affecting 25 percent of men and 40 percent of women in their eighties. If you can't get a good night's sleep, all kinds of neural and physiological systems begin to go haywire. Practicing good sleep hygiene is almost always more effective than medication. (pg. 161)

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There is a great variation in the degree to which people desire to learn once they are out of school. What differs across people is motivation and, to some extent, a worldview about who's in charge of your life. If you tend to think that the course your life takes is governed by other people, systems, and circumstances, you'll tend toward "accepting your fate" and not exerting yourself much to change things. (pg. 170)

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At any given time, 30 percent of the population is experiencing chronic pain - which is pain for more than three months. For older adults the number is closer to 40 or 50 percent. The odds of experiencing chronic pain at some point in your life are one in two. Many people assume that pain simply gets worse as we age, but this isn't true - it peaks then falls off. Chronic pain increases and peaks in our fifties and sixties, and then declines in our seventies and older. These numbers could arise because older adults become more stoic and stop complaining about it, or it could be that they simply don't have it anymore. (pg. 206)

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When we have a lot of food choices, we tend to overeat because the variety of flavors is enticing. It's the reason you always have room for dessert at a restaurant even when you're full. Even though you're full and you can't eat one more bite of steak, you're still interested in the cheesecake because it's sweet and that button hasn't been worn out in your brain yet. (pg. 276)

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Generally speaking, we don't remember anything from our first two years of life, and only a little before age six. People who claim to have vivid memories of early childhood are often mistaken and are reporting stories that were told to them by parents or siblings, or mistaking photographs of events for primary memories of those events. (pg. 284)

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Abandoning a particular activity, such as walking on uneven terrain or slicing vegetables, leads us to perceive ourselves as "someone who doesn't perform these kinds of actions anymore" and creates a growing self-image as a non-agent in the world. This can be one of the worst things about aging. Fear or trepidation about engaging in activities you've enjoyed your whole life just because you're "old" might not be a legitimate reason to abandon those activities - and may actually accelerate your entry into true "old age." (pg. 285)

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You may have seen where some people can get by with only a few hours of sleep per night. Although true, the proportion of people who can get along on fewer than five yours of sleep a night without showing major impairment is tiny - less than half of 1 percent. You may be one of those, but it is not at all likely that you are. The idea that older adults need less sleep is a myth. They tend to get less sleep, but they still need the eight hours that the rest of us need. (pg. 297)

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We have stigmatized sleep with the label of laziness. We want to seem busy, and one way we express that is by proclaiming how little sleep we're getting. It's a badge of honor. It's actually embarrassing to mention in public that we get eight hours of rest a night. Humans are the only species that deliberately deprive themselves of sleep for no apparent reason. (pg. 297)

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Given the time-dependent nature of hormonal release schedules that are governed by the circadian clock, what is the most important thing about sleep? To go to bed at the same time every night and wake up at the same time every morning. Even on weekends. This may mean forgoing late night parties if you're an early bird, or missing early-morning events if you're a night owl. By the time you reach old age, you will notice that inconsistency has become even more punishing. Even a slight change in the schedule - staying up an hour later than usual, for instance - can affect your memory, alertness, and immune system for days. (pg. 308)

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What is the ideal age to retire? Never. Even if you're physically impaired, it's best to keep working, either in a job or as a volunteer. Too much time spent with no purpose is associated with unhappiness. Stay busy! Not with busy-work or trivial pursuits, but with meaningful activities. Economists have coined the term unretirement to describe the hordes of people who retire, find they don't like it, and go back to work. Between 25 and 40 percent of people who retire reenter the workforce. (pg. 378)

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The single most important factor in determining successful aging is being conscientious. This means understanding why your body is changing. Adopting new lifestyle choices is difficult. But if you remember why the lifestyle change is important, you're more likely to stay with it, even when your motivation flags a little bit. Three additional factors that determine how well we age are more important than the rest. The first is childhood experiences, in particular of parental attachment and of head injury. If you had a concussion as a child, your chances of developing dementia in old age are increased by a factor of two to four. The second most important factor in retaining mental vitality later in life is to exercise in varied, natural environments. The third most important factor is social interaction. Interacting with others is among the most complex things we can do with our brains. (pg. 396)

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Remember that the world is changing, and those changes are at odds with your accumulated experience. Force yourself to update, to keep current with changes in the world. That involves getting out of your cocoon, doing things you wouldn't normally do, like learn to use a new cell phone app, or pre order and prepay for a coffee at your local cafe. These things can be annoying, but they will help prevent the mental rigidity that can accompany aging. (pg. 398)