With a little luck and serendipity, Sarah Mitchell engineered a remarkable life of health, happiness and success.

The one-time Big Island farm girl pushed her parents to send her to college, married, flourished as a restaurateur and businesswoman in Chicago and Hawaii, and became a first-time mother at age 56.

Mitchell’s perfect posture, fascinating storytelling and sharp-as-a-tack mind belie her years.

She celebrated her 101st birthday on Sept. 15.

Her genes, diet and exercise may partly account for her longevity. She’s the daughter of immigrants from Okinawa, known for its many centenarians. Her sister is 103.

She regularly eats natto (fermented soybeans), kimchi, pickled beets and takuan (pickled radish).

Until age 96, when her gym shut down due to the pandemic, she worked out daily on machines and took chair yoga classes.

Now the petite (4-foot, 6-inch-tall) Mitchell maintains her slim — not frail — figure with daily walks on her street.

Her wise words for a long and happy life: “It’s best to have happy thoughts and not to be depressed. There are times you lose yourself, but coming back to happy thoughts makes things better.”

BORN SARAH KISHIMOTO in 1923 in Piihonua, she was the only one in her family of six to get a college degree.

After graduating in 1941 from Hilo High School, the family moved to Honolulu, where she met Jiggy, a daughter of Neal Blaisdell, who planned to attend a university in Greeley, Colorado.

Mitchell said she was “a little above average” as a student. What she did excel in were social activities. “I had a lot of friends,” she said. “I had to be the center of attention. I demanded that.”

So her parents were surprised when she announced her desire to attend what was then Colorado State College of Education, now the University of Northern Colorado.

“My folks had to pinch and save, but my mother made sure I had some money,” she said.

Mitchell graduated in 1950 with a degree in nutrition. She also met her future husband, Edmund Mitchell, at the college.

“I think I chased him,” she said. “He was a rather bashful type. That’s what I liked about him.”

The couple married in 1955 and settled in his hometown of Chicago, where she worked for two years as a dietitian.

Sarah Mitchell conceived the idea of starting a Japanese-Hawaiian-themed restaurant in Chicago, and the couple opened the Diamond Head Restaurant in the late ’50s. They capitalized on its proximity to the Nabisco plant, serving American fare for lunch.

At night, the restaurant offered a unique dining experience with waitresses donning kimono serving sukiyaki. The concept drew a veritable who’s who of Chicago politicians and baseball players, as well as stars of the big screen.

On one occasion, Illinois Gov. Otto Kerner showed up with Danny Kaleikini. “The next day the paper was full of pictures of people dining at the Diamond Head Restaurant,” Mitchell said.

A number of celebrities frequented the restaurant, including Chicago Mayor Richard Daly, baseball player Joe DiMaggio and actors including Julie Newmar and Arlene Dahl.

AFTER THE Diamond Head’s run of about 20 years, the couple moved to Hawaii and bought other eateries.

The first was Haleiwa Sands, which was resold and renamed Jameson’s by the Sea. In the late ’70s, the couple bought Orange Tree, a healthy breakfast-­lunch spot in the former Amfac Center in downtown Honolulu.

Mitchell said she may have gotten her business sense from her mom, who bought acres of sugar plantation land, raised pigs and distilled okolehao (Hawaiian moonshine) from sugar cane.

Like her mom, Mitchell was industrious.

In her 70s, she worked as a receptionist for Honolulu Mayor Frank Fasi’s managing director. “You don’t see the director until you pass me, so I had a lot of gifts,” she said with a chuckle.

“I had a busy life,” she said.

But between the busyness, at age 56, Mitchell became a mom.

She had been helping a friend, Hollywood actress Jane Russell, with her World Adoption International Fund. Russell suggested Mitchell adopt a child, so the couple did.

When Sumi arrived in May 1978, the 8-year-old couldn’t speak much English.

Mitchell recalled her new daughter sadly looking out the window of their Portlock house, pointing across the ocean and uttering the words, “over there,” as if to say she wanted to return to the other side of the ocean.

Now 53 and married, Sumi Onodera said Mitchell initially had no idea how to be a mom.

Shortly after Sumi’s arrival, Mitchell upset the girl when she took her to a beauty salon and had her long locks cut. Then she placed the non-English-­speaking child in a YMCA program for the duration of the summer.

But Onodera said it’s how she learned English. “Three months of the YMCA, and I was ready for the fourth grade.”

Mitchell apparently got better as a mom. Today, Onodera is a wife, mother and lead business analyst for Kaiser Permanente — as well as a loving daughter.

In 2005, Mitchell moved in with her daughter; son-in-law, Chad Onodera; and grandsons Thomas-Joe, Carson-James and Spencer Onodera.

“I look forward to being with them,” she said of the grandkids. “They’re so good and so innocent.”

Mitchell loves her “mini-apartment” in their new two-story Kaneohe house. “I have my privacy when I want, and when I want company, I come upstairs.”

Her daughter cooks all her meals.

Mitchell attributed her continued happiness to her family.

“I’d be all alone if I didn’t have Sumi and the family,” she said, “so that makes me appreciate the family more.”