When I was a junior in high school, I decided to run for class president. It was an intensely competitive campaign, with something like eight candidates running for the position, including myself.

And I'll never forget when, at the height of the race, one of my classmates walked up to me, looked me straight in the eye, and told me she thought I didn't deserve to win.

Well, that was just the motivation I needed -- motivation to campaign even harder. I passed out more flyers advertising me as "a leader for a change," shook more hands, and otherwise tried whatever I thought it would take to win.

I did win, and I served a year as junior class president, before getting elected student council president in my senior year.

What I learned from that experience is an incredibly valuable lesson I took with me throughout my years in college and graduate school, and then into the working world. 

There have been many other times in my life and in my career where people have given me feedback that suggested -- and very often in black and white terms -- that I was unqualified to do something, or that I "didn't have the intrinsics" for a certain role. 

But, like that experience in high school running for class president, these sharp words, while initially demoralizing and demotivating, very often ended up forcing me to reflect hard on the feedback -- and then gave me the fuel I needed to prove them wrong.

There's a term for this that I heard recently in a video interview I recently watched on LinkedIn with Carla Harris, the Vice Chairman and Managing Director of Morgan Stanley. In the video, Harris shares how she became one of the most powerful women and black executives on Wall Street and in corporate America.

As an undergraduate at Harvard, a teaching fellow once told her, "Girl, whatever you do, don't major in economics." "When it was time to declare [my] major, I went straight to the...dean and wrote down 'economics.'"

"I'm negatively motivated. When you tell me I can't do something, I'm all over it."

After earning her MBA from Harvard, Harris joined Morgan Stanley as an associate in mergers and acquisitions. "Frankly, the reason I chose M&A was around the negative motivation. Everyone told me, 'don't do M&A' because they don't have a life, they're always on call, it's a miserable existence. So I said, 'aha,' I've gotta do M&A. I knew that if it was that busy and it had that kind of deal flow, and that kind of deal volume, I would learn the most in the shortest period of time."

"And that's advice I would give young professionals today. Do as much as you can in the first two or three years of your work life or your professional journey, and then step back and take a pause and think about all of the skills that you have acquired. Now recalibrate and think about whether you want to continue to apply them and learn in that lane, or you would like to take those skills and actually apply them to a completely different industry."

So, if you find someone telling you that you can't or shouldn't do something, especially if it's something you are strongly interested in, and you've proven to yourself that you have potential to succeed, don't let them sway you. Sure, you should reflect on the advice, especially if it comes from someone you respect and trust. 

But the only person who knows what you're passionate about and what you're truly capable of is yourself.