Billionaire "Shark Tank" star Mark Cuban was once in a band, the Not So Human Beings.
"There's a reason why you never heard of it," Cuban says, laughing, in a Amazon developer blog video published Monday. "It it was a great name. But, um, there was a time to quit."
The same holds true in business, says the tech entrepreneur. So how do you know when your business isn't working?
"When you don't have any customers? That's your answer," Cuban says. That's when you know what you are making is not going to become a successful business.
"One of the challenges of being an entrepreneur is that we all lie to ourselves. We are the best. We are the fastest. The greatest. The this-er, the that-est," Cuban says in the video. "If you find yourself always describing your company and how you are different in terms of 'er-s' and 'est-s,' you have got issues and you are probably lying to yourself.
"You have to be brutally honest. You have to ask yourself: If it wasn't me, if I was on the outside looking in, what would I say about this company? And if you are not able to do that, that's a bigger problem."
Having customers is the difference between being an inventor or maker and a successful business owner.
"The reality is there are a lot of great products and services that are undiscovered.... Because it's one thing to do something great. It is a whole other thing to ... be able to market and sell it," Cuban says.
But just because what you are working on is not going to be a successful business does not mean it is not worthwhile, Cuban says.
"Everybody defines success differently. I have always told people that if you can wake up in the morning with a smile on your face, excited about your day, knowing it is going to be a good day, you're successful. And so in terms of your business, you have got to live at some level right, but if you love what you are doing... it is not work," Cuban says.
For example, before Cuban co-founded his first company, AudioNet (which became Broadcast.net and sold to Yahoo for $5.7 billion in April 2000), he learned how to code.
"Early on, I had to teach myself how to program...and I would start writing these applications for customers. And I would start working on it...and I would look up and I had been sitting there for 24 to 26 hours not realizing that you know, I hadn't moved this whole time. I loved what i was doing" Cuban says.
"I was sleeping six guys, living six guys in a three-bedroom apartment ... I had a hole in the floorboard of my car. But I knew that there was a light at the end of the tunnel as long as I just kept on getting better at what I did. But had I not had the financial success, I still would have loved it. "
Disclosure: CNBC owns the exclusive off-network cable rights to "Shark Tank."
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