Americans spend decades building a retirement portfolio. But having enough money only solves one part of retirement. Research suggests what happens after you leave work may depend heavily on three things that never appear on a brokerage statement: control, relationships and purpose.

Retirement planning usually revolves around numbers. How much have you saved? When should you claim Social Security? Can your portfolio generate enough income? How much can you safely withdraw each year?

Those questions matter, but once the paychecks stop and the calendar suddenly opens up, retirees face another challenge: What exactly are you retiring to?

Bruce Feiler, author of A Time to Gather, offers a simple framework for answering that question. He calls it the ABCs: agency, belonging and cause. The idea is that a fulfilling retirement generally includes some control over your life, meaningful relationships with other people and something that gives you a reason to get up in the morning.

And one of those three may matter more than retirees realize.

Retirement Changes More Than Your Income

Leaving work doesn’t simply eliminate a paycheck. It can remove an entire structure that has quietly organized your life for decades.

Work determines when you wake up, where you go, whom you see and what problems you spend your time solving. It can also provide status, identity and a sense that somebody needs you. Retirement can remove much of that surprisingly quickly.

That’s one reason some people struggle even after achieving the financial retirement they planned for. A healthy portfolio can provide security and freedom, but it can’t automatically replace the routine, relationships and sense of purpose that came with a career.

That part of retirement has to be built separately.

The Three Pieces of a Fulfilling Retirement

Feiler’s ABC framework provides a useful place to start.

A: Agency

Agency is essentially control over your own life. For someone who spent 40 years answering to bosses, clients, deadlines and schedules, retirement can suddenly provide an extraordinary amount of freedom.

The question becomes what you do with it.

Agency can mean traveling, starting a garden, taking classes, moving somewhere new, working part time or finally tackling the project you’ve talked about for 20 years. It doesn’t need to be ambitious. What matters is retaining the feeling that you’re actively directing your life rather than simply allowing the days to fill themselves.

That can become more difficult as people age. Health problems, caregiving responsibilities and financial limitations can restrict choices. Complete control isn’t realistic, but maintaining meaningful choices wherever possible can still make a significant difference.

B: Belonging

This may be the most important part of the equation.

Retirement can quietly shrink your social world. Someone who once interacted with dozens of coworkers, customers or clients every week may suddenly spend considerably more time alone.

Research from the long-running Harvard Study of Adult Development has found a strong connection between the quality of people’s relationships and their happiness and health. That becomes especially relevant in retirement because leaving the workforce can disrupt many of the relationships and everyday interactions people previously took for granted.

Social planning, then, deserves to be part of retirement planning. Who will you see regularly? Where will you meet new people? Which friendships do you want to maintain? What organizations, clubs, churches, volunteer groups or community activities will keep you connected?

Those questions can become almost as important as deciding where you’re going to live.

C: Cause

The final piece is having something that feels worthwhile.

For decades, work often provides a built-in mission. There are projects to finish, people depending on you and problems that need solving. Retirement removes much of that structure, but it doesn’t necessarily remove the desire to feel useful.

A cause can take many forms. It might mean volunteering, mentoring younger people, helping with grandchildren, becoming involved with a community organization, working part time or pursuing a project you’ve always cared about.

It doesn’t have to change the world. It simply needs to give you something you consider worth doing.

Think About Your “Retirement Life Portfolio”

There’s an interesting financial analogy here.

Investors understand the danger of putting everything into one stock. Yet during our working years, many of us effectively do something similar with our lives. One institution can provide a large portion of our income, friendships, identity, daily routine and sense of accomplishment.

Then we retire and potentially lose all five at once.

A stronger retirement spreads those needs across different parts of life. Family can provide connection. Friends provide companionship. Hobbies provide stimulation. Volunteering can provide purpose. Exercise creates routine. Part-time work might provide income along with social interaction.

Think of it as a retirement life portfolio. Just as financial diversification reduces dependence on a single investment, life diversification reduces the pressure on any one person or activity to replace everything you once received from work.

The Retirement Risk That Doesn’t Show Up in a Financial Plan

Financial planners spend enormous amounts of time modeling longevity risk, inflation, healthcare expenses and the possibility of a market downturn early in retirement.

There’s another risk that’s much harder to put into a spreadsheet: social withdrawal.

It can happen gradually. You leave work and see former coworkers less frequently. Friends move away. Driving at night becomes less appealing. A spouse dies. Physical limitations make certain activities more difficult. Over time, your world can quietly get smaller.

That’s why waiting until you’re lonely to start building relationships may be a mistake. The years immediately before and after retirement can be an opportunity to strengthen friendships, reconnect with family and establish activities that regularly put you around other people.

Belonging doesn’t have to happen by accident. It can be planned for just like other parts of retirement.

You Don’t Need to Reinvent Your Entire Life

There’s also a danger in turning retirement into another achievement contest.

You don’t need to launch a nonprofit, travel to 40 countries or start training for a marathon at 72. Small things can provide plenty of structure and purpose: garden every morning, have lunch with friends every Thursday, volunteer twice a month, spend an afternoon with your grandchildren or teach someone a skill you’ve spent 30 years learning.

Retirement also doesn’t need to be completely figured out on your last day of work. It can develop in stages as you experiment with different routines and discover which activities and relationships actually make your life better.

Some plans won’t work. Interests will change. Health and family circumstances may change too. The ability to adjust may ultimately be as important as the original plan.

A Different Way to Prepare for Retirement

Financial security remains the foundation of a successful retirement. Money provides choices, protects against emergencies and makes many of the other parts of retirement easier.

But a retirement plan probably shouldn’t end with a portfolio balance.

Before leaving work, it may be worth asking three additional questions:

Agency: What do I want greater control over?

Belonging: Who will regularly be part of my life?

Cause: What will make my time feel worthwhile?

If one of those answers is missing, that’s something you can begin working on before retirement arrives.

After decades spent accumulating enough money to retire, the next challenge is figuring out how to use something even more valuable: your time.