Do you ever wonder if you’ll have a lasting effect on the world?

I think it’s hard-wired in some of us. Good thing, too; it probably has some deep connection to why we try so hard to raise our kids to be happy and successful.

But the truth is, your greatest impact might turn out to be something you never realize. 

The kind gesture to someone when he or she needs it most. The example you give to someone that leads them to pursue what turns out to be their calling.

Jeff Bezos just revealed the story behind one such person in his life.

It’s a 34-year-old tale, involving a college classmate he describes as “a humble, wonderful guy … the smartest guy at Princeton.” And as often happens, this classmate had no idea that Bezos even remembered him, until Bezos talked about him this week.

The story goes like this. When Bezos was in high school and college, he had his heart set on becoming a theoretical physicist. He enrolled at Princeton as a member of the class of 1986, one of about 20 students in the elite electrical engineering and computer science (EECS) program. 

“There were brilliant people everywhere," a classmate said, describing the program a few years ago. "We EECS geeks ... were a quiet, overwhelmingly male group of eccentric misfits."

Bezos fit right in. But although he was clearly very intelligent (he’d been the valedictorian of his high school class, and a National Merit Scholar), he by no means thought of himself as the smartest student in the program.

That honor, in his mind, went to a fellow student named Yasantha Rajakarunanayake, from Sri Lanka. And Bezos shared the moment that became truly clear.

He and his roommate, Joe, Bezos explained, had been working together for three hours on a particularly difficult partial differential equation, and getting nowhere. So they brought it to Yasantha.

He stared at it for a couple of minutes and came up with the answer without even writing anything down: “Cosine.”

Then he walked Bezos and Joe through the problem, writing three full pages of detailed algebra. Years before, he'd solved a similar problem years, Yasantha explained, and he remembered how he'd done it. So, he'd just “mapped this problem on to that problem."

To him, the answer had been "obvious."

“That was an important moment for me, because it was the very moment I realized I was never going to be a great theoretical physicist,” Bezos recalled in his talk. 

People laughed. And it's funny of course to think that if Yasantha and Bezos hadn’t had that exchange, perhaps Amazon wouldn’t be exactly what it is today.

But of course that's pretty theoretical. Instead, I think the real lesson from this story is Yasantha Rajakarunanayake's take on it today.

The two men hadn't talked since Princeton. Bezos also recalled him as "humble" and "wonderful," but Rajakarunanayake had no reason to think that Bezos particularly remembered him-;certainly hadn’t known that he’d had any kind of impact that Bezos considered important.

And he was clearly proud.

"Wow! Jeff is talking about me," Rajakarunanayake wrote on Twitter. "Amazingly he remembers interacting with me 34 years ago. What a memory! Also no Amazon if it weren’t for this, since he decided not to pursue physics!"

He continued: 

"Back in college, Jeff and I were just fellow students, and no one could have predicted what future would hold for us. Jeff remembers me as smart, humble and speaks fondly simply because I helped him with his homework."

But Rajakarunanayake also had an insight into why Bezos went on to become the world's wealthiest person.

Because remember-;Bezos had spent three hours trying to solve that problem before asking for help. And Rajakarunanayake recalled another time when Bezos stayed up all night working on another project, ultimately finding a solution that was better than the one Rajakarunanayake had come up with.

"Jeff was an excellent student, and a very persistent, tenacious one. That is unique to him," he recalled to an Indian newspaper, The Print. He "will not give up like most of us would when presented with a challenge."

That's probably the ultimate combination: not just smart, not just tenacious, but both together in a single package. And that's as good an explanation as any for why Bezos built Amazon, and you and I didn't.

By the way, Yasantha Rajakarunanayake is doing fine. He went on after Princeton to earn a doctoral degree at ?Caltech, "and received 54 patents in the U.S." with 40 others currently pending, according to The Print. "Currently, he is based in California and serves as a senior director for MediaTek, a Taiwanese semiconductor firm."