Confidence is knowing what you can do and being secure in your ability to do it. Having and displaying confidence at work can show you're capable of rising to the challenges of your job, boost motivation and focus, and keep stress at bay. Here's how to stay inspired.

You can employ both verbal and nonverbal tactics to display confidence at work by embracing a positive attitude, acknowledging your achievements, communicating your concerns, and using positive body language like good posture and smiling. If you need a little boost, here are 12 motivational quotes. Put them in your email signature, print them out and hang them over your computer, or just write them down on strategically placed sticky notes for instant inspiration.

1. "It is confidence in our bodies, minds and spirits that allows us to keep looking for new adventures, new directions to grow in, and new lessons to learn — which is what life is all about."
— Oprah Winfrey, media mogul and television personality

2. "When you have confidence, you can have a lot of fun. And when you have fun, you can do amazing things."
Joe Namath, Hall of Fame football player

3. "Optimism is the faith that leads to achievement. Nothing can be done without hope and confidence."
— Helen Keller, author and political activist

4. "If you're presenting yourself with confidence, you can pull off pretty much anything."
— Katy Perry, singer

5. "Confidence comes not from always being right but from not fearing to be wrong."
— Peter T. McIntyre, painter and author

6. "Whether you come from a council estate or a country estate, your success will be determined by your own confidence and fortitude."
Michelle Obama, first lady of the United States

7. "I always did something that I was a little not ready to do. I think that’s how you grow. When there's that moment of, 'Wow, I'm not so sure that I can do this,' and you push through those moments, that’s when you have a breakthrough. Sometimes, that's a sign that something really good is about to happen. You're about to grow and learn a lot about yourself."
Marissa Mayer, CEO, Yahoo

8. "One important key to success is self-confidence. An important key to self-confidence is preparation."
— Arthur Ashe, Grand Slam tennis champion

9. "Surviving a failure allows you more self-confidence. Failing is a great learning tool, but it must be kept to an absolute minimum."
Jeffrey Immelt, CEO, General Electric

10. "Don't wait until everything is just right. It will never be perfect. There will always be challenges, obstacles and less-than-perfect conditions. So what? Get started now. With each step you take, you will grow stronger and stronger, more and more skilled, more and more self-confident, and more and more successful."
— Mark Victor Hansen, motivational speaker and co-creator of Chicken Soup for the Soul book series

11. "Inaction breeds doubt and fear. Action breeds confidence and courage. If you want to conquer fear, do not sit home and think about it. Go out and get busy."
Dale Carnegie, inspirational writer and lecturer

12. "The most beautiful thing you can wear is confidence."
— Blake Lively, American actress and model

If all else fails, and you find your confidence at work flagging, remember what Christopher Robin told his good friend Winnie the Pooh: "You're braver than you believe, and stronger than you seem, and smarter than you think."