To be self-confident is to believe in oneself, to be assured that you are who God says that you are, to trust in one's abilities and to be kind to oneself.
Our children need to know that they are great. They are valued. They are loved. They have much to offer; and yes, they belong in the spaces that they occupy.
For those times when the confidence needs a boost, trust that 'there's a book for that too'.