They get their happiness from within. Happiness is a critical element of confidence, because in order to be confident in what you do, you have to be happy with who you are. People who brim with confidence derive their sense of pleasure and satisfaction from their own accomplishments, as opposed to what other people think of their accomplishments.
Building confidence is a journey, not a destination. To become more confident you must be passionate in your pursuit of a greater future.
The Definite Major Purpose drives to this point: to be happy with who you are in your greater future.