How old is your son? Do you have any idea why he might lack confidence?

I just learned that praise makes them afraid to fail. They want the praise and afraid not to get it. Read Punished by Rewards, Raising Our CHildren, Raising Ourselves, and Mothering magazine article "Getting Our of the Way http://naomialdort.com/articles3.html

Praise makes children want to get more praise so they do the thing that gets it and become fearful of not getting it. Self-esteem actually goes down.