We all have limits. Some are physical. Some are mental. Some limits we simply can't do anything about.

But in most cases, our limits are self-imposed.

Here's an example of a self-imposed limit: effort. We all have this little voice inside us that says "I've done enough" or "I'm exhausted; there's no way I can do more," and so we stop.

But that little voice lies: With the right motivation, or under the right circumstances, we can always do more. Stopping is actually a choice. We don't have to stop; we choose to stop. (As ex-Navy SEAL Ray Care told me, "When you truly have nothing left in the tank, you either black out, pass out, or die. That's it. Otherwise, you have more in you.")

The same is true for skill. Once you reach a certain level of expertise, your rate of improvement typically slows ... and it's natural to assume you're near your limit.

But you really aren't. You just think so, because you've started comparing your present self to your past self and not to what is actually possible. You've started to look back to see how far you've come instead of looking forward to see just how far you can still go.

You assume you're as good as you're likely to ever be. And so, often unconsciously, you stop trying.

Here's a great example, showing how often, without even realizing it, we can set self-imposed limits.

Last year I went to Victory Lane Karting in Charlotte, North Carolina, with a number of Nascar executives and three actual racers: Alon Day, EuroNascar series driver and 2016 Israeli Athlete of the Year; Ty Majeski, 2016 ARCA Midwest Tour champion; and Ross Chastain, Xfinity series driver, occasional truck series driver, and all-around good guy.

I've been to kart tracks before and typically finished well compared with other weekend warriors. But three professional drivers? On the very first practice lap they all flashed past me going into a series of S-turns.

I knew they would be fast, but their speed seemed surreal. I couldn't imagine going that fast.

But I settled in and tried to find the best lines, the best braking points ... practice is all about experimenting, so I did my best and finished the practice session with the fifth quickest time out of 10 people.

I was about half a second behind a non-racer. Not bad. Except Alon, Ty, and Ross were nearly five seconds faster.


While we took a break, the other non-racers chatted with each other. I went straight to Ross and asked him how he was so quick.

He looked out at the track for a moment. "Were you flat out through the S's?" he asked.

"Um, no," I said, narrowing my eyes with skepticism. Pedal to the metal on a tight track might seem fast, but it's usually not. In some places you have to go slow in order to be fast. "I didn't think I could."

"Sure you can," he said. "Go in wide, tap the inside corner of the first turn, then tap the wall just before the narrowest point on the next one. That's the line you want to take. The back end might slide a little on the exit of the last turn and you may kiss the wall, but that's OK."

OK, I thought. Easy for your Nascar-driver ass to say.

Oddly enough, though, it was easy for my skeptical ass to actually do. On my first qualifying lap I used the line he recommended, entered the first S-turn flat out ... and never had to lift. That alone made me much faster, since I carried extra speed into the straightaway and through the following right-hand sweeper.

What changed? My skill wasn't the problem. My self-imposed limit was the problem. I didn't think it was possible to go flat out ... so it wasn't. Once I knew it was possible, it was possible.

Nothing changed except my perspective -- and, as a result, my skill.

I had stopped thinking about going a little faster than I had earlier and started thinking about trying to be as fast as Ross. I was no longer my benchmark; Ross was.

After qualifying -- and using a few other tips Ross gave me about a few other turns -- I was fourth fastest behind Alon, Ross, and Ty, each of whose lap times had improved by about half a second over the practice session.

My lap times had improved by over three seconds.

For the race we lined up in qualifying order, 10 feet separating each kart. As the laps wound down, Alon, Ross, and Ty gradually eased into the distance. I did manage to lap all but one of the other karts, and kept from being lapped by the fast guys.

But for the most part I just tried to race the track and drive the way Ross would. Of course I couldn't -- but I tried, because he was my benchmark.

And that mental shift made me faster -- my fastest lap was almost a second quicker than my fastest qualifying lap -- because I forgot my self-imposed limits and instead focused on trying to achieve what was actually possible.

And you can do the same.

Stop comparing yourself to yourself. Stop comparing yourself to the people around you. Go see a superstar in action. Whether it's a speaker, a musician, a performer, an athlete, an entrepreneur ... find a way to expose yourself to exceptional skill, exceptional expertise, and exceptional talent.

I've ridden with professional cyclists; the experience, while humbling, automatically ratcheted my performance bar higher. I've worked with one of the queens of data analysis; the experience, while humbling, automatically ratcheted my own problem-solving expectations much higher.

Spend time with a superstar. Experiencing, in person, what is actually possible will automatically ratchet your own internal limits to a higher level. While you may never be as good, when superstar performance is your bar, you automatically set your goals higher -- and that makes you achieve more. Stop comparing your present self to your past self.

Start comparing your present self -- regardless of how far you think you have already come -- to what is actually possible.

Stop looking back. Start looking forward to see how far you can still go.

And then work hard to get there.

You may never be as talented as the absolute best in the field or pursuit you choose ... but you will definitely achieve much more than your self-imposed limits allowed you to think was ever possible.