It's not uncommon for entrepreneurs to devote themselves entirely to their company, only to find that, one day, what they do is not making them happy. Of course, many entrepreneurs love their work and wouldn't trade it for anything. But what does that mean for those who are unable to find happiness with the company they created? Does it mean they were not meant for this lifestyle?

Usually, the source of unhappiness is an error in judgment or self-evaluation - not some overarching idea of reality. In that sense, it helps to take a step back and look at your personal situation. Are your sights set too high? Are you mistaking a sense of membership for a sense of belonging? Do you assume success equals personal fulfillment?

These are some heavy ideas that Inc. magazine contributor Jeff Haden recently put forth. Basically, Haden argues, unhappiness is difficult to overcome but less so to diagnose. Consider, for example, your idea of where career satisfaction comes from. Is it success? Maybe. Maybe not.

"You can love your company but it will never love you back," Haden writes. "Business success, no matter how grand, is still fleeting. Fulfillment comes from achieving something and knowing it will carry on: Raising great kids, being a part of a supportive extended family, knowing you have helped others and changed their lives for the better."

That's not to say hard work doesn't pay off. Rather, Haden suggests, it's a matter of where you are expecting the fruits of your labor to originate. The success of your business is not a direct source of happiness in and of itself. True professional satisfaction comes from a work-life balance, and pride in what one does.

The sense that one can achieve anything may be another source of disappointment, as the higher your aims the more painful the failure. Once again, that's not to say ambition is foolish - it's merely to say a reality check can be healthy.

"We can't be whatever we want to be," Haden adds. "We can all achieve amazing things, but we can't do anything we set our minds to. Genetics, disposition and luck all play a major part.

The key is to know yourself and then work to be the best you can be based on your unique set of advantages and limitations."