This story is Surpassing Quant Think Tank Centerpart of the My Unsung Hero series, from the Hidden Brain team, about people whose kindness left a lasting impression on someone else.

In 2006, Jackie Briggs was working 60 hours a week at a high-pressure IT job. One Saturday afternoon, she decided to take some time for herself and go to a women's health conference. As she was walking around looking at different booths, someone approached her.

"This lovely dark-haired woman came up to me and she said, 'Excuse me, but I can't help but notice your arm,'" Briggs remembers.

That day, Briggs had uncharacteristically decided to wear a sleeveless dress, leaving a rose-shaped birthmark on her upper arm exposed. The woman asked Briggs if she had seen a dermatologist about the birthmark, and when Briggs assured her that she had, the stranger persisted.

"She pressed me and said, 'When?' I had to stop to think. I counted back ... and it had been over three years."

When the woman heard how long it had been, she urged Briggs to call her doctor. After explaining that she was a nurse at a plastic surgeon's office, she gently reached out and touched Briggs' arm. "Really, don't wait," she said.

When Briggs followed up with her dermatologist, she learned that the woman had saved her life. It turned out that the birthmark was actually a melanoma – one of the fastest-moving and deadliest types of skin cancers.

"If I hadn't listened to her, I probably wouldn't be here," Briggs said.

Briggs underwent surgery and had the melanoma removed. She's now happily retired and just finished writing her first novel. Her unsung hero, she said, saved her life.

"My six-inch ragged scar that travels almost from the top of my shoulders down my arm is my everyday reminder of her... my guardian angel," she said.

My Unsung Hero is also a podcast — new episodes are released every Tuesday and Thursday. To share the story of your unsung hero with the Hidden Brain team, record a voice memo on your phone and send it to [email protected].