The Center for Disease Control & Prevention lists developmental milestones for the first five years of life – “skills such as taking a first step, smiling for the first time, and waving “bye bye.”” After five years, evidently, all bets are off, and it’s up to us to figure out the appropriate next steps. Now that we’re living longer, with yet more longevity on the horizon, what should the developmental goals be for our lives?

The pandemic taught us this, if nothing else: a lot of how we choose to live is completely made up rather than dictated by necessity. Cubicle farms and open-plan offices now seem like self-inflicted indentured servitude; long commutes a relic of barbarian civilization. All the successful adaptations we’ve made over the past two-plus years have made us more keenly aware than ever that there might be more successful choices we could make for ourselves if only we took the time to look.

The truth, though, is that we’ve been modifying our concepts of age-stage appropriate milestones all along the way with improved technology and lengthening lifespans. Biological concepts like “adolescence” didn’t exist until the twentieth century, and it was a marketing slogan in the 1950’s that introduced “the golden years,” instantly reframing the later years of life as a time for leisure rather than misery.

This is the truth behind jokes about “40 being the new 30” and “60 being the new 40.” As we live longer, our chronological years don’t seem to correspond with past markers of age and milestones for health, education, family and careers.

This can be disconcerting, since we tend to establish our life goals based on what other people are doing. If everyone else in our cohort is going to college, we go too. If our friends and family tend to marry by the time they’re thirty, we seek to find a life partner by then as well. And so on.

According to London Business School professors Lynda Gratton and Andrew Scott, things are about to become even more confusing as “The 100-Year Life” becomes the norm. For roughly the last half century, we’ve thought of our lives unfolding in three stages of education, career and retirement in the so-called 20-40-20 model. As 100-year lives become the norm, rather than the exception, and as personalized medicine makes it likely that we’ll remain healthy for most of that time, we’re going to need to rethink this model.

Harvard geneticist David A. Sinclair argues in his bestseller Lifespan that the challenges may be even greater than that, with normal life and health spans approaching 120 years within a few decades.

The rub, of course, is that none of us can count on enjoying a fully allocated share of this new-normal longevity. As economists observe, life is “stochastic,” meaning so variable from person to person that we have no clue when we ourselves will die. Disease affects each of us differently, and accidents will continue to cut down healthy adults in their prime.

This means we simply have to do our best at striking a healthy balance between our desires today and our needs tomorrow, which is the essence of personal financial planning. We establish financial goals with timeframes and dollar amounts and formulate how to achieve them, knowing that we could get hit by the train tomorrow or die peacefully in our sleep on our hundredth birthday.

Fortunately, a lot of the things that are good for ourselves today are the very things that will improve our lives tomorrow. Eating a healthy diet gives us more energy and makes us feel better today; it also increases the odds that we’ll feel similarly in later years. Establishing good savings habits now means we can accumulate a rainy-day fund for impending emergencies as well as financial resources to supplement or replace income in later years.

Thus, here is a thought exercise: if you knew for certain that you would be one of the people who lived a healthy 100 years, would it change any of your plans today and going forward?

It’s easy to see how someone in their 40’s might realize that they weren’t too old, after all, to go back to school and train for a new career. Or how someone in their 60’s might decide it was still worthwhile to sign up for piano lessons. With another forty years ahead of them, they might get pretty good at it!

On the other hand, this could be an unsettling question if we’ve made choices based on assumptions derived from current social norms. If we decided to grit it out in the job we don’t like because “traditional retirement age” is only a few years off, then we might not want to hear that there were other options.

However, the pandemic showed us how easily these norms can be upended. Do we really want to follow the established scripts and timetables without first asking whether they make sense for us and at least consider alternatives?

In the most recent episode of The Atlantic podcast series How to Build a Happy Life, Arthur C. Brooks and Rebecca Rashid talk with psychiatrist Robert Waldinger, head of the Harvard Study of Adult Development, one of the longest-running studies of human happiness on record, about the key elements for happy living. (A New Formula for Happiness)

Waldinger cited the developmental theorist, Bernice Neugarten, “who had a theory about being on time or off time” and “that, developmentally, we care a lot about what our community around us considers normal for the age that we are at, and that it affects us if we feel we are “off time”—if we’re not doing the things right now that other people our age are supposed to be doing.”

Waldinger advised “pull[ing] back from that and to try to listen to yourself . . Because it is your life. Nobody else is going to live your life. And so the world can tell you, “You ought to be doing this at this point in your life.” But you cannot let that be the thing that is your sole driver.”

The beauty of personal financial planning is that it teases out the assumptions and scripts that run our lives to determine whether we still want to follow them. Once you start asking questions, moreover, you don’t have to look far to see how many other possibilities there are for what you might do and by when.

While it may be true that many skilled employees follow a three-stage model of education, career, and retirement, variations abound. There’s the schoolteacher who took time off, then retrained to become a lawyer; the firefighter who retired with a pension in his forties, then started a business that he continued to run far past traditional retirement age. Of course, the examples of non-conformist artists are legion, and while we might be tempted to dismiss them as outliers, perhaps it's no coincidence that Picasso was still painting and Pablo Cassals still playing his cello well into their nineties, having followed their own muse.

Marcus Aurelius asked, “What is it in ourselves that we should prize?” After listing what it is not, including “moving in herds,” he says,