While all those are important factors in the success of your business or career--and therefore your earning power--here's one factor you probably haven't considered:

Whom you marry.

Researchers at Washington University in St. Louis found that people with relatively prudent and reliable partners tend to perform better at work, earning more promotions, making more money, and feeling more satisfied with their jobs.

That's true for men and women: "Partner conscientiousness" predicted future job satisfaction, income, and likelihood of promotion (even after factoring in the participants' level of conscientiousness).

According to the researchers, "conscientious" partners perform more household tasks, exhibit more pragmatic behaviors that their spouses are likely to emulate, and promote a more satisfying home life, all of which enables their spouse to focus more on work.

As one researcher said, "These results demonstrate that the dispositional characteristics of the person one marries influence important aspects of one's professional life." (In non-research-speak, a good partner both sets a good example and makes it possible for you to be a better you.)

I know that's true for me. My wife is the most organized person I know. She juggles family, multiple jobs, multiple interests--she's a goal-achieving machine. Her "conscientiousness" used to get on my nerves, until I realized the only reason it bugged me was because her level of focus implicitly challenged my inherent laziness.

I finally realized the best way to get more done was to actually get more done, and she definitely helps me do that.

And I try to do the same for her. Since my daily commute is two flights of stairs, I take care of most of the household stuff: laundry, groceries, cleaning (I don't do all of the cleaning, but I make sure it gets done), etc., so when she comes home she can just be home.

So, while she's still much more conscientious and organized than I am, she's definitely rubbed off on me in a very positive way.

Which of course makes sense: As Jim Rohn says, we are the average of the five people we spend the most time with--and that's particularly true where our significant others are concerned.

Bad habits rub off. Poor tendencies rub off. We all know that. But good habits and good tendencies rub off too.

Plus, if one person is extremely organized and keeps your household train running on time, that frees the other up to focus more on work. (Of course, in a perfect world, both people would more or less equally share train-engineer duties so that both can better focus on their careers, whether those careers are in the home or outside.)

Keep in mind I'm not recommending you should choose your significant other solely on the basis of criteria like conscientiousness and prudence. As the researchers say, "Marrying a conscientious partner could at first sound like a recipe for a rigid and lackluster lifestyle." Nor am I suggesting you end a relationship if you feel your partner is lacking in those areas.

But it does appear that having a conscientious and prudent partner is one ingredient in the recipe for a better and more rewarding career.

So instead of expecting your partner to change, think about what you can do to be more supportive of your significant other. Maybe you can take on managing your finances, or take care of more household chores, or repairs, maintenance, or schedules. After all, the best way to lead is by example.