Take for instance, you want to rise before dawn say at 5.0 clock. You knew it is good for you. Unless you will, to apply the principle, you will not be able to do it. On Day 1, apply your will to get up. If you succeed, do the same on Day2. As you go on, you experience that your will power is being enhanced. This enhances the confidence in your SELF. This is Self-Confidence. After practicing it for considerable period of time, you see that rising before dawn is as natural as breathing. Here comes forth a vital conclusion that will power increases only by its application in day-to-day life.
Following is an excerpt from a book, which i love to read again and again, being mismarized by its wisdom.
"Willingness denotes a very important mental state. It indicates that a person has evaluated himself and sees the need for change, and that he is prepared to act to bring about such change."