If you're a nice person, you probably think that being nice works to your advantage in the office. After all, how could it be any other way? Genuinely nice people are well liked. They're generally easy to work with. They care about others and tend to have good values. In a fair and just world, that sort of behavior should be rewarded. Right?

Not necessarily. Too often, nice, competent people get passed up for promotions. Instead, the plum job goes to the prima donna or the person who plays politics. The bonus is bestowed upon the squeaky wheel or the obnoxious go-getter. In this environment, the nice guy really does finish last. It's frustrating because it goes against everything we were taught as a children about the Golden Rule.

What nice people may not realize is that they're too nice, and that being too nice can seriously stymie their career growth and success, says Russ Edelman, a SharePoint consultant and co-author of the book, Nice Guys Can Get the Corner Office: Eight Strategies for Winning in Business Without Being a Jerk (Portfolio, 2008.) "The people in business who suffer from nice guy syndrome are not achieving their true potential," he says.

The problem with being too nice, according to Edelman—who comes off as a very nice guy—is that you're a doormat and people take advantage of you. Nice people are too concerned about pleasing others and not making waves that they don't stand up for themselves.

Edelman cites a nice man he interviewed for his book, who was vying for an executive position. The nice man was well-respected and well-liked in his company, and had a very good shot at the job. Of course, someone else was competing for the position. When the nice man was asked in an interview about his competitor, according to Edelman the nice guy said he thought his competitor would do a fantastic job. The nice contender wound up writing a letter of recommendation for his competitor because he didn't want to cause a stir by vying for the executive-level job, says Edelman. End result: The competitor got the job, and the nice guy remained in his spot on the corporate ladder.

"The nice guy is forever putting the oxygen mask on someone else before putting it on himself," says Edelman.