We all know the abysmal statistics on women in leadership roles. And that sexism, and our society's general discomfort with women in positions of authority are largely to blame. But women ourselves can--and often do--undermine our own leadership in the way we approach leadership and the confidence we do or don't project. That analysis comes from Daina Middleton, leadership coach an author of Grace Meets Grit: How to Bring Out the Remarkable, Courageous Leader Within.

This doesn't mean that women's lack of advancement is our own fault, but it does mean we might be inadvertently making things worse. Ask yourself how many of these common mistakes you've made. Personally, I've made most of them:

1. Counting on your work to speak for itself.

Promoting your own value and telling people about your accomplishments and worth can feel awkward, especially for women. Many of us fall back on the idea that if we work extra-hard and do a really excellent job at everything we take on, that excellence will be noticed and rewarded without our having to promote ourselves, which takes many of us outside our comfort zone. "That's why women work more on competence than on confidence," Middleton says. "They think, 'If I'm just better, I won't have to confront this core issue.'"

Unfortunately, it doesn't work that way. If you want to succeed in a leadership role, you must learn to project confidence as well as competence. Perceptions of competence are highly subjective, Middleton says--people are more likely to think you're good at what you do if you yourself act like you know this to be true. Besides, being able to project confidence is an essential skill for any leader.

2. Hesitating to take on the status of leadership.

"Women prioritize establishing and maintaining relationships and men prioritize gaining and maintaining status, and each of those translates directly into a leadership style," Middleton says. "But when you establish a relationship with someone, then step out of equal status it disrupts that relationship. That's the core discomfort women have, and it's why we work more on competence."

3. Taking longer to make a decision so as to gather all points of view.

This is a mistake I myself have made big-time, and it's something women commonly do, Middleton says. "Decisiveness is the most recognized leadership behavior," Middleton says. "Whereas women will be very inclusive in their leadership and decision-making approach. They might sacrifice speed to be sure they're being inclusive and they may be judged as not having leadership skills."

Does this mean you have to make quicker decisions? Not necessarily, Middleton says. But if you delay a decision so as to gather more viewpoints, make sure you are also seen to be taking immediate action. Send a note to your boss or a message to your organization that says what you've done so far, what you plan to do next, and when. "Many women miss doing that," she notes.

4. Not voicing strong opinions.

You may really know your stuff. Unfortunately, Middleton says, "There's lots of research that shows having a strong opinion counts more than knowing what you're talking about."

How do you address this problem without sounding like a blowhard? Middleton recommends having the facts at your command. Once you do, you can state your point of view with confidence and authority because you know you can back up whatever you say.

5. Not learning how to project calm and confidence while speaking.

"Learn to speak the language of status and confidence," Middleton advises. "Confidence is in the way you speak, your tone, your deliberateness and calmness, and how you portray your body language," she says. Look for a practice that will put you back in a place of calm authority when you feel your confidence slipping.

That practice will be different for everyone. For some women, it's simply slowing and evening out their breathing, for others it might be picturing the other people in the room naked. Middleton says her practice is to think about riding her horse, remembering that when a horse is skittish, sitting calmly in the saddle, taking up space, and speaking in a calm voice will help it settle down. Figure out what mental practice will help keep you projecting confidence before the next time you find yourself in a stressful leadership situation.

6. Not embracing your own power.

Leadership is about power. But most women are uncomfortable really taking on the power of a leader. "When I ask women to come up with someone in a powerful position who had an impact on their lives, it's never another woman," Middleton says. That may partly result from the general shortage of women in powerful positions, but it's still noteworthy.

She encourages women to think of power as the ability to empower others rather than having power over them. "Power is potential realized," she says. "Part of confidence is embracing your own internal power. You can't be a leader without it."