The cliché in entrepreneurship and business is this: “The difference between success and failure comes down to how bad you want it.”

That’s not true.

You could want something really, really badly and still not get it. Conversely, you could be in the right place at the right time and have “success” fall right into your lap. Work ethic certainly shouldn’t be discounted, but the truth is, pure hours-in does not necessarily mean rewards-out. As much as people want to believe they are 100% correlated, they are not. There is a fair amount of strategic thinking that has to accompany those long hours spent slaving away.

The difference between success and failure then, as with any pursuit, comes down to a very different question—and the question is hard to answer, which is why so few people take the time to consider it. They would rather just put their head down and grind, than pick their head up and question where they were headed in the first place.

The Question: Are you replaceable?

You see, any long-term success is not just the result of hard work. It’s hard work mixed with the awareness that who you are, what you do, and what you bring to the table cannot be replaced. Because in any situation, if there is a cheaper, better, faster, smarter option available, that’s who people are going to go with. So whatever it is you “achieve” will be very short lived if a month, a year, or five years from now someone else comes along doing the same thing except better.

So many companies and entrepreneurs fail because they do not take the time to ask this question. They see themselves without an expiration date. They assume that the revenue they make this month is now the standard and will continue into the future as long as they keep waking up hitting the pavement. But that is a false assumption—and one that leaves a blind spot in your field of vision.

Work ethic doesn’t mean anything if someone else comes along and says, “I can do this better, for less.”

When you are running your own business, or when you are trying to make a name for yourself as an entrepreneur, you need to constantly ask yourself how you can continue to reinvent what it is you do. Every day, ask yourself if you are replaceable—and be honest with your answer. Some people avoid this question because it makes them feel vulnerable. Others simply don’t take the time to ask it in the first place. But by knowing you are, in fact, replaceable, you will start to ask yourself the tough questions related to how you can continue to evolve.

Case in point: Remember Blockbuster? They were really good at moving movie rentals. They were great at putting their head down and doing that one thing really well. They were a successful brand and company. But they faltered because they didn’t stop and ask themselves, “Are we replaceable?”

Today, Blockbuster no longer exists because Netflix came along and did exactly what Blockbuster did, but better, cheaper, and more efficiently.

The lesson here is: work hard and stay focused, but remember it’s not all about grinding.

It’s about keeping one eye on what needs to get done right now, and another eye on the long game.

“Am I replaceable?”Opinions expressed here by Contributors are their own.

Nicolas Cole is a writer and essayist, and Top Writer on Quora with over 10,000,000 views. His work has been published in Time, Forbes, Fortune, Inc., The Huffington Post, Business Insider, and more. He is a columnist for Inc Magazine and is best known for writing true stories about self-development. You can follow him on Twitter @Nicolascole77