As far as I know, confidence is broken down in YOUR ABILITY and PAST ACHIEVEMENTS.
Knowing that your good at something and looking back on a great achievement.
2 other good things for the old confidence are Not careing what other people think of you, when you think like this, its hard for people to knock you down.
And, when you have a story about something or news about something, dont tell anyone. Its your little secret and you can laugh at them not knowing.
Much more can be added to this I know but just a few thoughs.
Barry.