I had a great mentor early in my career give me advice that I’ve heeded until now, which is that you should have a running list of three people that you’re always watching: someone senior to you that you want to emulate, a peer who you think is better at the job than you are and who you respect, and someone subordinate who’s doing the job you did — one, two, or three years ago — better than you did it. If you just have those three individuals that you’re constantly measuring yourself off of, and you’re constantly learning from them, you’re going to be exponentially better than you are.

How do you define success? Is it when you have a job that pays you a certain amount of money each year? Maybe it’s when you own a home of a certain value in a particular part of town? Or is it when you have the freedom to spend more quality time with your family? Or do you compare yourself to your peers, playing this constant game of relative superiority?

Once upon a time, Chris Fussell was an officer with the US Navy SEALs. These days, he is a managing partner and leader at McChrystal Group, which describes itself as “an elite advisory services and leadership development firm.” He co-authored Team of Teams with some of his McChrystal Group colleagues a couple of years ago.

Cited in the recent book Tools of Titans by Tim Ferriss (with the foreword by Arnold Schwarzenegger of all people), what you read above was the response the former Navy SEAL gave to the “4-Hour Workweek” proponent when asked who he thought of when he hears the word “successful.”

His response brings up a very valid point. While a rivalry can motivate you, comparing yourself only to your peers is insufficient. You don’t know where you’re going. And comparing yourself only to your mentors and heroes is insufficient too, but you don’t know how to get to where they are today. By looking at a subordinate, a contemporary, and a superior, you gain a broader perspective into the bigger picture.

Perhaps the greater challenge, then, is to stave off any feelings of envy or jealousy when you compare yourself to someone who is doing better than you are. It’s not about becoming them. It’s about learning from them and defining your own path. As the late Kurt Cobain once told us, “Wanting to be someone else is a waste of the person you are.”

Who do you look to for inspiration and guidance? Is “success” an ethereal concept that is simultaneously almost within our grasp and just out of reach? How will you know you’re successful?