A chronotype is an individual’s natural, internal pattern of sleep and wakefulness, which determines whether they’re a “night owl” or an “early bird.” Emanuel emphasizes that one’s chronotype dictates the optimal timing for sleep, work, and decision-making. Readers are advised to understand and respect their personal chronotype to improve sleep quality and daily functioning, while noting that it doesn’t determine the total amount of sleep needed.

Cognitive maintenance is the practice of actively “exercising” the brain throughout life to delay the age-related onset and speed of cognitive decline. It involves engaging in new and mentally challenging activities to strengthen neural connections and help preserve cognitive function with age. The author presents this as a complement to cognitive reserve, the brain’s accumulated resilience built through earlier education and enriching activity.

Cognitive reserve is the brain’s accumulated resilience to age-related functional decline, built primarily through education and intellectually enriching activities. A higher cognitive reserve acts as a protective buffer, meaning that it takes longer for the inevitable deterioration of brain function to become noticeable or debilitating.

Crystallized intelligence is the accumulated knowledge, vocabulary, and overlearned skills that are well preserved as a person ages. This form of intelligence relies on long-term memories and explains why older individuals can remain proficient in familiar tasks, such as speaking their native language or recalling well-known stories, even as other mental faculties decline.

The Dunbar number is the theoretical cognitive limit to the number of meaningful social relationships a person can maintain, estimated to be around 150. Emanuel uses this concept to explain that because our capacity for friendship is finite, we must be intentional about cultivating our social circles rather than relying on superficial online connections.

Emanuel describes emotional wellness behaviors as the cultivation of strong family, friend, and social relations, which he argues are more critical to longevity and well-being than physical behaviors. In the book, this category also includes avoiding self-destructive risks, maintaining social interactions, and sustaining mental engagement.

Fluid intelligence is the ability to think critically, reason about new problems, and develop new skills, which tends to decline with age. This form of intelligence relies on processing speed, working memory, and brain plasticity, making it more challenging for older people to learn unfamiliar skills or solve novel problems.

Novel information activities are new and challenging hobbies, such as learning a new language or playing a musical instrument, that help maintain mental acuity. The author recommends these activities for cognitive maintenance because their complexity engages a wide variety of mental functions, building new neural connections more effectively than repetitive tasks like crossword puzzles.

Orthosomnia is an unhealthy obsession with achieving perfect sleep, often caused by fixating on data from consumer sleep-tracking devices. Emanuel warns against this condition, noting that the anxiety it produces undermines restful sleep and that how one feels upon waking is a more accurate measure of sleep quality.

The author describes physical wellness behaviors as the three components of wellness most commonly emphasized by popular writers and gurus: eating, exercise, and sleep. While these are essential, Emanuel argues that they represent only half the story and are ultimately less impactful on longevity and overall well-being than emotional wellness behaviors.

A repetition barrier is the critical obstacle to forming a new wellness habit, defined as the difficulty of sticking with an activity long enough for it to become automatic. Emanuel argues that willpower runs out fastest once a habit feels tedious rather than new, so he recommends scheduling, social accountability, and small rewards to carry the reader past that stage—making persistence harder to sustain, and more consequential, than the initial motivation to begin.

A “schmuck move” is the author’s colloquial term for a self-destructive action that carries a high risk of serious, irreversible harm without sufficient precaution. Examples include smoking, texting while driving, and using tanning salons. Emanuel places avoiding these behaviors first in his framework because the harms they cause cannot be undone by any other wellness practice.

Emanuel’s six wellness behaviors are the book’s organizing framework of six practices, ranging from avoiding self-destructive risks to getting sufficient rest, that he presents as achievable without overhauling daily life. The list comprises avoiding self-destructive risks, cultivating social relations, expanding the mind, eating and drinking healthily, exercising well, and getting sufficient rest.

A social initiator is a person who takes on the burden of starting conversations with strangers and new acquaintances. Adopting this role, the author argues, is a rewarding way to build weak social ties and feel more connected since most people want to connect but are too shy to begin.

Temptation bundling is a psychological strategy for habit formation that pairs a desirable activity (a “want”) with a necessary wellness behavior. In research that the author cites, participants could only listen to a popular audiobook while at the gym, which successfully increased gym attendance.

Ultra-processed foods are industrially formulated foods, also called “junk food,” that are high in sugar, salt, and unhealthy fats while being low in nutrients. The author identifies these foods as “hyperpalatable” and addictive, linking their habitual consumption to obesity, faster cognitive decline, and an increased risk of chronic disease.

Weak social ties are connections with people outside one’s immediate social circle, such as acquaintances from work, community groups, or daily errands. Research that Emanuel cites shows that even brief, minimal interactions with these individuals, like chatting with a barista, improve well-being and create a valuable sense of belonging.

The “wellness industrial complex” is the author’s term for the vast industry of books, podcasts, influencers, and products that promote costly, time-consuming, and often unproven wellness regimens (5). This complex is criticized for turning wellness into an obsession and a full-time job, rather than a simple means to a more fulfilling life.