One of the books I'm currently reading is "The Magic of Thinking Big" by David J Schwartz. This has been full of good nuggets.
One of the chapters discusses building confidence. Below are 5 simple steps to take action to help that process: 1. Be a front seater 2. Eye contact 3. Walk faster 4. Speak up 5. Smile big
Bottom line is that like most things that are worth doing, it takes impact action to build confidence.