Former President Jimmy Carter recently died in his home in Plains, Ga., at the age of 100. As the 39th president of the United States, he held the distinction as the nation’s longest-living commander-in-chief.

Carter, the only centenarian alumnus of the Oval Office, was a naval officer, peanut farmer, and humanitarian. He began receiving hospice care in his home in February.

Here are some of his pearls for living a long, fulfilling life:

Exercise and tennis routine

Carter adhered to a routine exercise regimen, according to his grandson. Last year, Jason Carter told Time that his grandfather used to play tennis every day and jogged everywhere he went, especially while traveling. When he couldn’t jog anymore, he biked.

“If he got to a new city that he had never been to before, whether there was Secret Service or not, he would say, ‘Hey, is there a bike?’” Jason Carter told Time.

Regular exercise is key to healthy aging, especially as older adults lose muscle mass. It helps reduce the risk of chronic conditions like diabetes, obesity, and heart disease, and it can also relieve stress and improve mental health outcomes. Kirk Erickson, PhD, director of Translational Neuroscience at AdventHealth Central Florida, previously told Fortune that exercise can also keep the brain’s hippocampus, which is responsible for memory, intact and healthy.

Tennis, in particular, kills two birds with one stone: It keeps people active and connected to others, reducing the risk of loneliness and social isolation.

Read more about how to stay active as you age.

Happy marriage

The former president was married to Rosalynn Carter for 77 years. The duo hold the title of the longest-married presidential couple in the nation’s history. Their lifelong partnership heavily contributed to their happiness and long-term health.

Jason Carter told Time that his grandfather would most likely attribute his longevity to Rosalynn, who died last year.

“Rosalynn was my equal partner in everything I ever accomplished,” former President Carter said in a statement about his wife posted to The Carter Center following her passing. “She gave me wise guidance and encouragement when I needed it. As long as Rosalynn was in the world, I always knew somebody loved and supported me.”

Feeling connected and purposeful boosts happiness, which serves people into older age. Strong social connections are also an antidote to anxiety, depression, and dementia, according to the U.S. Centers for Disease Control and Prevention (CDC).

Carter would also jog alongside Rosalynn and, while in office, around the White House lawn.

Rosalynn and Jimmy Carter jogging — “Rosalynn was my equal partner in everything I ever accomplished,” former President Carter said.

Read more about how to foster connections at any age.

Giving back to others

Alongside Rosalynn, former President Carter prioritized giving back and serving others. He led the Jimmy & Rosalynn Carter Work Project for Habitat for Humanity for over 30 years.

“Together, they’ve worked alongside over 108,100 volunteers who have built, renovated, or repaired more than 4,447 homes in 14 countries, all while raising awareness of the critical need for affordable housing,” the project’s team wrote in a statement this week.

Finding a larger purpose and mission sustains people as they age. Carter and his wife championed social justice, housing, and equity issues, and they spent their time post–White House on improving these issues globally. In the 1980s, The Carter Center, established to mitigate global disease burden and resolve conflict, launched a global campaign to eradicate Guinea worm disease.

In The Coming of Age, Simone de Beauvoir writes that aging gracefully “is to go on pursuing ends that give our life a meaning—devotion to individuals, to collectives, to causes, social, political, intellectual or creative work.” One study also found that giving back and volunteering can lower people’s stress, giving them purpose and passion. Moreover, maintaining a positive outlook on aging—often driven by a sense of purpose and motivation—can add years to your life.

Jimmy Carter was the first president to live to 100. Here are his 3 science-backed strategies for longevity