Are you working long hours at your start-up company and still worrying each month about whether you can cover your mortgage payment? If so, you may be doing something wrong, according to Victor Green, author of How to Succeed in Business by Really Trying, and a serial entrepreneur who's launched several successful companies and spent the past 15 years consulting with other entrepreneurs.

"If you have your own business, irrespective of what it is, it should have the same single objective, to make money," he says.

Instead, he says, too many entrepreneurs fall in love with their product or with the idea of running their own company, he says. How can you tell when you aren't paying yourself enough? Here are some signs to watch for:

1. You could make more working for someone else.

"If you're not making more than you would at a job, I think you're a fool because of the additional responsibility and risk," Green says. "When you work for someone else, you take home your salary. When you have your own business, you're at the end of a very long line, behind the landlord, the utilities, the cell phone company, and so on. I've talked to people making $2,500 a month from their business. I tell them they could earn more than that stacking boxes in a grocery store."

2. You're not seeing steady improvement.

If your business isn't paying you as much as you'd like today, can you see definite signs that it will be earning more in the near future? "You may be starting to see greater interest from people," Green says. "You're getting 10 inquiries a week, and you were getting three a month ago." These kinds of things can tell you that a better income is on the horizon.

"But if you're sitting there saying, 'I've done everything I should on Twitter, and I don't understand why more customers aren't coming,' you've got a problem," Green says.

3. You don't know how your business is doing financially.

Here's a simple test: If someone sat down with you and asked you a series of questions about your company's revenue, expenses, and profits (or losses) for the previous month, quarter, and year, could you answer within a few minutes, using your accounting software? If not, Green says, you don't know enough about your own business.

"I mentored someone who had a coffee store," he says. "They asked, 'How do I know if we're doing better?' I told them, 'You need traffic and you need sales,'" Green says.

The coffee store began monitoring traffic and sales. "They did that for a month, and then they began making slight changes," he says. "They started doing sandwiches. They started doing fresh juices. And they were able to tell whether those things were helping. If you stay on top of the numbers, there are many things you can do to monitor and improve your performance. But it's amazing how many people don't know very much about their own business's performance."

If you follow the numbers, you can tell when your business is succeeding and when it's time to shut it down before it drags you into a financial hole, he says. And there should be no shame in shutting down, if that's the right decision. "Running a business isn't right for everyone," he says.

Last month, Victor Green shared his thoughts on the Top 3 Bonehead Moves Entrepreneurs Make.