Mark Cuban. Billionaire. NBA team owner. Shark Tank star. Consummate salesperson. (And, as I saw in person, a very nice guy.)

To what does he attribute his success?

According to Cuban: "It's not about money or connections. It's the willingness to outwork and outlearn everyone."

Yep. No hacks. No shortcuts. Cuban -- a guy with the results to show for it -- clearly feels that success is based primarily on working hard. Incredibly hard.

Yet whenever I write about how success is often based on outworking other people -- both in terms of effort and in terms of hours spent -- many people email to say that working smarter, not harder, matters more.

That's a fair point, but one that also misses the larger point.

Work Harder and Smarter

Yes, you do need to constantly search for ways to work smarter -- but you also need to find ways to work harder.

Successful people are the proof. 

Bill Gates evidently never slept, never changed clothes, never did anything but code and maneuver and strategize. In an industry filled with incredibly smart people -- where incredibly smart was and is commonplace -- he rose to the top by also working incredibly hard.

Apple CEO Tim Cook starts his morning routine -- not just his morning, his morning routine -- at 3:45 a.m. General Motors CEO Mary Barra gets to the office by 6 a.m. Best-selling author Dan Brown -- The Da Vinci Code, etc. -- gets up at 4 a.m., has a smoothie and a cup of bulletproof coffee, and then writes away. 

(Of course, what time you get up has nothing to do with your productivity. As I wrote in an article that hundreds of thousands of people read recently, success is all about what you accomplish -- and, just as important, how you choose to accomplish it. And how do most successful people choose to accomplish things? By working really, really hard.)

Successful people already work smarter. They don't work mindlessly or inefficiently or ineffectively. Where success is concerned, working smarter is a given. Extremely successful people work smarter, and they work harder.

Other people write to say that luck plays a big part in success. Or timing. Or any number of other factors.

And they're right.

But none of us can control luck. None of us can control timing. None of us can control all those other factors.

But there is one thing we can always control:

How hard we work.

Hard Work Is the Great Equalizer

Everyone defines success differently. If you happen to define success by measures like professional achievement and fortune and fame, hard work is the great equalizer.

But here's the thing: If your definition of success leans heavily toward the quality of your personal relationships, or maintaining a positive work-life balance, or making a meaningful difference in the lives of others, hard work is again the great equalizer. Great relationships require significant effort. Work-life balance requires significant effort. Making a meaningful difference in other people's lives requires significant effort. 

People with great relationships work harder than most at those relationships. People who make the most of their "life" time work harder than most at improving the quality of the "life" hours they carve out. People who stand out for serving others work harder than most to leverage their skills and experiences; that's how they make such a meaningful difference. 

And here's the most important thing: You may not be smarter than everyone else. You may not be as talented. You may not have the same great connections, the same great environment, or the same great education.

If you're on the downside of advantage, you may have none of those things.

But you can always, always, always work harder than everyone else.

Hard work can always be your difference.

Mark Cuban committed to outworking and outlearning everyone around him.

You can too.

Do that, and whether at work, or in your personal life, or wherever your definition of success leads you, you may not accomplish everything you hope for, but you will accomplish a lot more.

Because how hard you work is the one thing you can always control.